Martini at last included in list for revel (7)
I believe the answer is:
roister
'for revel' is the definition.
(both can mean to party)
'martini at last included in list' is the wordplay.
'at last' says to take the final letters.
'included in' indicates putting letters inside.
'list' becomes 'roster' (a roster is a list or register).
The last letter of 'martini' is 'i'.
'i' placed inside 'roster' is 'ROISTER'.
(Other definitions for roister that I've seen before include "Have noisy fun" , "Engage in party activity" , "Carouse" , "Noisy reveller" , "riot" .)