Unusual places to conceal large knife (7)
I believe the answer is:
scalpel
'knife' is the definition.
(scalpel is a kind of knife)
'unusual places to conceal large' is the wordplay.
'unusual' indicates anagramming the letters.
'to conceal' is an insertion indicator.
'large' becomes 'l'.
'places' is an anagram of 'scapel'.
'scapel' going around 'l' is 'SCALPEL'.
(Other definitions for scalpel that I've seen before include "Surgeon's tool" , "Surgical instrument" , "Theatrical knife?" , "A surgeon's knife 97)" , "sharp knife" .)