Give a reason for changing axle pin (7)
I believe the answer is:
explain
'give a reason' is the definition.
(I've seen this before)
'changing axle pin' is the wordplay.
'changing' indicates anagramming the letters.
'axle'+'pin'='axlepin'
'axlepin' is an anagram of 'EXPLAIN'.
'for' acts as a link.
(Other definitions for explain that I've seen before include "Elucidate, make clear" , "Tell us how" , "Show the meaning of, make clear" , "Justify" , "Make (something) clear" .)