Idiot catches nose removing old attire (7)
I believe the answer is:
twinset
'attire' is the definition.
(type of clothing)
'idiot catches nose removing old' is the wordplay.
'idiot' becomes 'twit' (both can mean a stupid person).
'catches' is an insertion indicator.
'removing' indicates named letters should be taken away.
'old' becomes 'o' (abbreviation as in OT - Old Testament).
'nose' with 'o' taken out is 'nse'.
'twit' enclosing 'nse' is 'TWINSET'.
(Other definitions for twinset that I've seen before include "Wear associated with pearls?" , "Matching cardigan and jumper worn together" , "Matching cardigan and jumper when worn at the same time" , "Kit worn to match" , "clothing" .)