A convict gets up for a fete (4)
I believe the answer is:
gala
'fete' is the definition.
(I've seen this before)
'a convict gets up for a' is the wordplay.
'a convict' becomes 'lag' (I've seen this before).
'gets up' says the letters should be written in reverse.
'for' says to put letters next to each other.
'lag' in reverse letter order is 'gal'.
'gal'+'a'='GALA'
(Other definitions for gala that I've seen before include "Social occasion with special performances" , "Festive celebration" , "Festive occasion - variety of apple" , "Sports meeting" , "Swimming competition" .)