A swell in the avenue (5)
I believe the answer is:
heave
'a swell' is the definition.
(I've seen this before)
'in the avenue' is the wordplay.
'in' indicates the answer is hidden within the clue.
'HEAVE' is hidden within 'the avenue'.
(Other definitions for heave that I've seen before include "Pitch" , "Produce (a sigh); lift" , "Swell; throw" , "Tug-of-war cry" , "Gasp" .)