What's tight becomes relaxed (5)
I believe the answer is:
thaws
'becomes relaxed' is the definition.
I can't tell whether this definition defines the answer.
'what's tight' is the wordplay.
'tight' indicates anagramming the letters (tight can mean drunk).
'whats' anagrammed gives 'THAWS'.
Can you help me to learn more?
(Other definitions for thaws that I've seen before include "friendlier times?" , "As role of Morse was to become" , "Starts to unfreeze" , "(Of snow) melts" .)