'a key lead' is correct and usable in written English.
You could use it in almost any context when referring to something that could lead to an important result. For example, "The detective had a key lead that might help solve the mystery."
Despite a few major opportunities – a supporting role in Paradise Road, a key lead in Oscar and Lucinda – it took Shekhar Kapur's surprisingly gritty period thriller to announce Blanchett's arrival.
"By this point in the film," as the CNN national-security analyst Peter Bergen wrote recently, "the audience has already seen that the C.I.A. has employed coercive interrogation techniques on an al Qaeda detainee that produced a key lead in the hunt for bin Laden.
Having joined Great Britain cycling in 2002, Sutton played a key lead role in the squad in the buildup to the Beijing Olympics and then the London Games after Brailsford became increasingly involved with Team Sky and he has continued to head up the day-to-day running of the squad since 2012.
Compound 15 emerged as a key lead and showed significant ability to inhibit growth factor-induced receptor phosphorylation in SK-BR-3 cells (IC50 = 54 nM) and cellular proliferation in vitro (IC50 = 14, 58, and 58 nM for BT474, N87, and SK-BR-3 respectively).
Ives's penchant for writing fugues with each voice beginning in a different key led Horatio Parker, his teacher at Yale, to say that he shouldn't be "hogging all the keys at once".
For the past eight years, Weissman has been a key engineering lead for the CRM giant, joining the company when it only had 10 developers in 2002.
Once the user has narrowed his or her search to a specific species, the key leads to a page with multiple images of the species, and links to all of the images of the species in the database (Table 1: Best Practice 1a).
After someone slipped him a key, he led Mr. Rivera and a TV crew into a building there, scuffled with a guard and confronted the director, all on camera.
"Look what's in here!" July said as she showed me the secret compartments in the cabinet's drawers — one hidden drawer held a key that led to another interior chamber.
Issues relating to a key supplier led to the decision, indicating perhaps that the company had simple cash flow problems.
The use of MIMO was a key that led to success of IEEE 802.11n, HSPA, and LTE, and now MIMO continues its journey with the LTE-Advanced.
