Fruit became more trendy (7)
I believe the answer is:
rosehip
'fruit' is the definition.
(fruit of a rose plant)
'became more trendy' is the wordplay.
'became more' becomes 'rose' (eg a number which rises becomes more).
'trendy' becomes 'hip' (both can mean fashionable).
'rose'+'hip'='ROSEHIP'
(Other definitions for rosehip that I've seen before include "Hedgerow or garden fruit" , "Red fruit" , "Part of plant" , "Fruit from flower providing syrup" , "Fruit on wild plant" .)