The phrase "a substantial leg" is correct and usable in written English.
It can be used in contexts where you are describing a significant or considerable part of something, often in a metaphorical sense or when discussing physical attributes.
Example: "The table was designed with a substantial leg to ensure stability and support for heavy items."
Alternatives: "a significant leg" or "a considerable leg".
Now this, he thought, was something to hold on to, a mantra for life, a substantial leg-up on the greasy pole of progress, the first block in a philosophy predicated on the glorious assumption of certainty.
One of the many effects of this overvaluation, as most 20-somethings and many 30-somethings know, has been to put home ownership – certainly in southern England – a long way beyond their reach, unless they band together or rely on an increasingly substantial leg-up from their parents.
The substantial leg and thigh portion of the bird was pounded almost flat, then seared, the skin crisping to bronze, and roasted to succulence.
The additional variables prioritized by the physiotherapists in the MDT group were signs of nerve root involvement and substantial leg pain.
The additional variables prioritized by the chiropractors in the SM group were no signs of nerve root involvement and not substantial leg pain.
(PS We do not call the more substantial legging either a tregging or a jegging – it's common. PPS The peep-toe clogs have nothing much to do with legging-world, but I bought them, I love them, they're very fashion, and that is that).
Furthermore, the study demonstrated a substantial decline in leg extensor muscle power in the ACL operated limb 7 weeks after surgery despite the fact that the rehabilitation program started immediately after surgery.
We need to build a substantial lead.
"The LLM in Law & Entrepreneurship gave me a substantial and noticeable leg-up on other first year associates practicing corporate law in general and particularly those working in my firm's tech group.
But we need to travel to Spain for the second leg with a substantial advantage.
