First of gashes in uncovered elbow (5)
I believe the answer is:
nudge
'elbow' is the definition.
(I know that elbow is a more specific form of nudge)
'first of gashes in uncovered' is the wordplay.
'first of gashes' becomes 'g' (nst letter of 'gashes').
'in' means one lot of letters goes inside another.
'uncovered' becomes 'nude' (I've seen this in another clue).
'g' placed inside 'nude' is 'NUDGE'.
(Other definitions for nudge that I've seen before include "Push; prompt" , "Prod gently with elbow" , "Dig with elbow" , "Poke gently with elbow" , "Give a reminder" .)