Bear walking along and not returning (10)
I believe the answer is:
paddington
'bear' is the definition.
(Paddington Bear, character in children's books)
'walking along and not returning' is the wordplay.
'walking along' becomes 'padding' (pad can mean to walk along).
'and' means one lot of letters go next to another.
'returning' is a reversal indicator.
'not' reversed gives 'ton'.
'padding'+'ton'='PADDINGTON'
(Other definitions for paddington that I've seen before include "London station - famous bear" , "London rail terminus" , "A figure child might want for Play" .)