Noun's disguised hiding place in puzzle (7)
I believe the answer is:
nonplus
'puzzle' is the definition.
('nonplus' can be a synonym of 'puzzle')
'noun's disguised hiding place' is the wordplay.
'disguised' indicates anagramming the letters.
'hiding' means one lot of letters goes inside another.
'place' becomes 'pl' (I've seen this in other clues**).
'nouns' anagrammed gives 'nonus'.
'nonus' enclosing 'pl' is 'NONPLUS'.
'in' acts as a link.
(Other definitions for nonplus that I've seen before include "Perplex, confound" , "Put at a loss; confuse" , "Perplex totally" , "Perplex completely with negative and positive" , "Disconcert, confound" .)