What's out, melts (5)
I believe the answer is:
thaws
'melts' is the definition.
('thaw' can be a synonym of 'melt')
'what's out' is the wordplay.
'out' indicates anagramming the letters (out can mean wrong or inaccurate).
'whats' is an anagram of 'THAWS'.
(Other definitions for thaws that I've seen before include "friendlier times?" , "(Of snow) melts" , "Starts to unfreeze" , "As role of Morse was to become" .)