Child impressed by odd treatise describing part of cowboy's apparel (7)
I believe the answer is:
stetson
'apparel' is the definition.
(Stetson is an example)
'child impressed by odd treatise describing part of cowboy's' is the wordplay.
I cannot really understand how this works, but
'child' could be 'son' (male child) and 'son' is found within the answer.
'part' could be 'te' (te is a kind of part) and 'te' is present in the answer.
The remaining letters 'st' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for stetson that I've seen before include "Large hat" , "Hat with broad brim and high crown" , "Hat for country-and-western singers, Texan oil magnates, etc." , "Hat with wide brim and high crown, maybe a cowboy's" , "No tests (anag.)" .)