Cheesy month with rotter at home (2,6)
I believe the answer is:
au gratin
'cheesy' is the definition.
(I've seen this before)
'month with rotter at home' is the wordplay.
'month' becomes 'Aug' (abbreviation for August).
'with' says to put letters next to each other.
'rotter' becomes 'rat' (synonyms).
'at home' becomes 'in' ('I'm in' can mean 'I'm at home').
'aug'+'rat'+'in'='AU GRATIN'
(Other definitions for au gratin that I've seen before include "Of cooking, done with crust of melted cheese" , "Cooked with browned breadcrumbs and, sometimes, cheese" , "Covered with breadcrumbs or grated cheese" , "Crumby" , "Scattered" .)