Initial resistance got round by a bunch of fives (5)
I believe the answer is:
first
'initial' is the definition.
(similar in meaning)
'resistance got round by a bunch of fives' is the wordplay.
'resistance' becomes 'r' (electronics abbreviation).
'got round by' means one lot of letters goes inside another (some letters go around others).
'a bunch of fives' becomes 'fist' (slang term).
'r' placed into 'fist' is 'FIRST'.
(Other definitions for first that I've seen before include "Position for gold" , "Top degree class" , "at the outset" , "Primary" , "Before all else" .)