It's not so hot in the jug (6)
I believe the answer is:
cooler
I believe this clue is a double definition.
'it's not so hot' is the first definition.
(I've seen this before)
'the jug' is the second definition.
(thesaurus)
'in' acts as a link.
(Other definitions for cooler that I've seen before include "Nick" , "It's not so hot" , "more sophisticated" , "Prison - less warm" , "less enthusiastic" .)