Crucial to check body's attractive (13)
I believe the answer is:
prepossessing
'attractive' is the definition.
(similar in meaning)
'crucial to check body's' is the wordplay.
I cannot really understand how this works, but
'body' could be 'posse' (I have seen 'Body of constables' mean 'posse' so perhaps 'body' could also mean 'posse') and 'posse' is located in the answer.
The remaining letters 'pressing' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for prepossessing that I've seen before include "Fetching" , "winning" , "looking good" , "Attractive" .)