A vessel containing mostly lush fruit (7)
I believe the answer is:
apricot
'fruit' is the definition.
(apricot is a kind of fruit)
'a vessel containing mostly lush' is the wordplay.
'vessel' becomes 'pot' (pot is a kind of vessel**).
'containing' means one lot of letters goes inside another.
'mostly' means to remove the last letter.
'lush' becomes 'rich' ('rich' can be similar in meaning to 'lush').
'rich' with its last letter removed is 'ric'.
'pot' placed around 'ric' is 'pricot'.
'a'+'pricot'='APRICOT'
(Other definitions for apricot that I've seen before include "Orange fruit" , "tree" , "Juicy fruit" , "Yellow fruit" , "Small, peach-like fruit" .)