Suggestion about start of return journey (4)
I believe the answer is:
trip
'journey' is the definition.
(trip is a kind of journey)
'suggestion about start of return' is the wordplay.
'suggestion' becomes 'tip' (tip is a kind of suggestion).
'about' is an insertion indicator.
'start of' suggests taking the first letters.
The first letter of 'return' is 'r'.
'tip' placed around 'r' is 'TRIP'.
(Other definitions for trip that I've seen before include "day out?" , "In close confrontation" , "Journey; make a mistake" , "Run - dance - tumble" , "Accidental misstep" .)