It's not so hot in the jug (6)
I believe the answer is:
cooler
I believe this 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' is the link.
(Other definitions for cooler that I've seen before include "Nick" , "It's not so hot" , "more sophisticated" , "Prison - less warm" , "less enthusiastic" .)