The phrase "a relevant portion of" is correct and usable in written English.
It can be used when referring to a specific part of a larger text or discussion that is pertinent to the topic at hand.
Example: "In the report, a relevant portion of the data highlights the trends in consumer behavior over the past year."
Alternatives: "an important part of" or "a significant section of".
Here's a relevant portion of the Analyst Day transcript, per Seeking Alpha.
Statistics [1] show that a relevant portion of the world's population owns a digital camera and can capture pictures.
To summarize, in septic revision surgery a relevant portion of the susceptible prosthesis is not protected against bacterial reinfection.
We here report the crystal structure of a relevant portion of RipA, containing its catalytic-domain and an extra-domain of hitherto unknown function.
Even in well structured reports from the US, a relevant portion of the primary headaches could not be classified, and therefore, 20%[19]to36%[13][13] of the acute patients were not given a diagnosis in the ED.
Furthermore, a relevant portion of them are not satisfied with the management of their disease, partly because of the poor efficacy of treatments and partly because of the difficulty to get in touch with the specialist.
However, we cannot completely exclude the possibility that a small but relevant portion of the PARK2-BECN1 interacomplexomplex in mitochondria involves PINK1.
The Argus Leader has a transcript of the relevant portion of the interview.
He did not discuss details of the compromise, but a draft of the relevant portion of the budget obtained by The New York Times changes language added to state law last year while Mr. Spitzer was governor.
The methodology consists of building a boarding/alighting hall of a metro car and the relevant portion of the platform in front of the hall.
In such an unstructured conformation, the relevant portion of the VAMP's cytoplasmic domain could stretch up to 130Å.
