Thaw breaking out, don't you think? (4)
I believe the answer is:
what
'out don't you think?' is the definition.
I can't tell whether this defines the answer.
'thaw breaking' is the wordplay.
'breaking' is an anagram indicator.
'thaw' with letters rearranged gives 'WHAT'.
Can you help me to learn more?
(Other definitions for what that I've seen before include "That which - come again!" , "I beg your pardon" , "I didn't hear" , "Which thing?" , "Word used in a question" .)