The most common and most likely answer to this crossword clue is the 2 plus 4 letter word IN PART
I've seen this crossword clue in Independent
I
N
P
A
R
T
More clues leading to the result IN PART
Buddy explains!

The straight part
We know that "Assuming role/somewhat" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case assuming role/somewhat = in part.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.