Hybrid melon, one scooped out for party (4)
I believe the answer is:
gala
'party' is the definition.
(I've seen this before)
'hybrid melon one scooped out' is the wordplay.
'hybrid melon' becomes 'galia'.
'one' becomes 'i' (Roman numeral).
'scooped out' is a deletion indicator.
'galia' with 'i' taken out is 'GALA'.
'for' is the link.
(Other definitions for gala that I've seen before include "Special social or sporting occasion" , "Special performance" , "fair" , "Public festivity" , "Mix" .)