Rummy party backed by attractive type (6)
I believe the answer is:
oddish
'rummy' is the definition.
'party backed by attractive type' is the wordplay.
'party' becomes 'do' (do is a kind of party).
'backed' says the letters should be written in reverse.
'by' is a charade indicator (letters next to each other).
'attractive type' becomes 'dish' (informal term for an attractive person).
'do' in reverse letter order is 'od'.
'od'+'dish'='ODDISH'
(Other definitions for oddish that I've seen before include "Rather strange" , "Fairly unusual" , "a little rum" , "A bit peculiar" , "kind of crackers" .)