Pleasantly warm (7)
(Other definitions for summery that I've seen before include "Hot" , "of the season" , "concerning part of the year" , "description of August in UK?" , "Like August, say" .)
'pleasantly warm' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for toasty that I've seen before include "nice and warm?" , "Hot food" , "Pleasantly warm" , "snack" , "Sandwich" .)