Mean to change gear behind short avenue (7)
I believe the answer is:
average
'mean' is the definition.
(I know that mean can be written as average)
'change gear behind short avenue' is the wordplay.
'change' indicates an anagram.
'behind' is a charade indicator (letters next to each other).
'short avenue' becomes 'ave' ('short' indicates an abbreviation).
'gear' is an anagram of 'rage'.
'rage' after 'ave' is 'AVERAGE'.
'to' acts as a link.
(Other definitions for average that I've seen before include "Normal amount" , "It's common" , "Usual - mediocre - mean" , "just like any other" , "Mean - typical" .)