Fruit became more fashionable (7)
I believe the answer is:
rosehip
'fruit' is the definition.
(fruit of a rose plant)
'became more fashionable' is the wordplay.
'became more' becomes 'rose' (eg a number which rises becomes more).
'fashionable' becomes 'hip' (I've seen this in another clue).
'rose'+'hip'='ROSEHIP'
(Other definitions for rosehip that I've seen before include "Fruit of the briar" , "Part of plant" , "Berry for syrup" , "Hedgerow or garden fruit" , "Wayside fruit" .)