Ached badly in cold season? Get a jacket (11)
'a jacket' is the definition.
(windcheater is a kind of jacket)
'ached badly in cold season?' is the wordplay.
'badly' indicates anagramming the letters.
'in' indicates putting letters inside.
'cold season?' becomes 'winter' (I've seen this before).
'ached' is an anagram of 'dchea'.
'dchea' inserted within 'winter' is 'WINDCHEATER'.
'get' acts as a link.
(Other definitions for windcheater that I've seen before include "warm clothing", "jacket".)