A rep travelling in fruit (4)
I believe the answer is:
pear
'fruit' is the definition.
(I know that pear is a type of fruit)
'a rep travelling in' is the wordplay.
'travelling' indicates anagramming the letters.
'in' is an insertion indicator.
'rep' anagrammed gives 'per'.
'a' inserted within 'per' is 'PEAR'.
(Other definitions for pear that I've seen before include "Juicy fruit" , "Tasty fruit to reap" , "Fruit sounds like two of a kind" , "Fruit tree" , "Tapering fleshy fruit - reap it" .)