I’d year the reverse of cold and ill — delightful (7)
I believe the answer is:
idyllic
'delightful' is the definition.
(I've seen this before)
'i'd year the reverse of cold and ill' is the wordplay.
'year' becomes 'y'.
'the reverse of' says the letters should be written in reverse.
'cold' becomes 'c' (eg on taps).
'and' says to put letters next to each other.
'c'+'ill'='cill'
'cill' backwards is 'llic'.
'id'+'y'+'llic'='IDYLLIC'
(Other definitions for idyllic that I've seen before include "Blissfully peaceful" , "Peaceful and deligthful" , "Charming, picturesque" , "Very peaceful and picturesque" , "Unspoiled and perfect" .)