Dress his Gran better (7)
I believe the answer is:
garnish
'dress' is the definition.
(I know that dress can be written as garnish)
'his gran better' is the wordplay.
'better' indicates anagramming the letters (with an improved letter-order).
'his'+'gran'='hisgran'
'hisgran' anagrammed gives 'GARNISH'.
(Other definitions for garnish that I've seen before include "Sharing (anag) - dress" , "Decorate food for table" , "Decorate with herbs" , "Embellish food" , "Decorate, embellish" .)