Of suitable girth, perhaps (5)
I believe the answer is:
right
'of suitable' is the definition.
I can't judge whether this definition defines the answer.
'girth perhaps' is the wordplay.
'perhaps' is an anagram indicator.
'girth' anagrammed gives 'RIGHT'.
Can you help me to learn more?
(Other definitions for right that I've seen before include "Most favourable" , "Fit" , "Prerogative" , "Sound" , "It's what you deserve" .)