Fitting that unwieldy girth (5)
I believe the answer is:
right
'fitting' is the definition.
(I've seen this before)
'unwieldy girth' is the wordplay.
'girth' anagrams to 'RIGHT'.
But, I'm not clear how this is indicated.
'that' acts as a link.
Can you help me to learn more?
(Other definitions for right that I've seen before include "The hand to the east when facing north" , "Equitable" , "correctly" , "Morally good; rectify" , "It's what you deserve" .)