Nothing out, it's inferred, drained (3,2)
I believe the answer is:
all in
I believe this clue is a double definition.
'nothing out it's inferred' is the first definition.
(without nothing out everything is in)
'drained' is the second definition.
(thesaurus)
(Other definitions for all in that I've seen before include "without any extras" , "At an inclusive price; exhausted" , "wasted?" , "Ready to drop" , "price covering the lot" .)