Perhaps let us in for the instrument (7)
I believe the answer is:
utensil
'the instrument' is the definition.
(I've seen this in another clue)
'perhaps let us in' is the wordplay.
'perhaps' indicates an anagram.
'let'+'us'+'in'='letusin'
'letusin' is an anagram of 'UTENSIL'.
'for' is the link.
(Other definitions for utensil that I've seen before include "Item, eg for kitchen" , "knife, maybe" , "A kitchen pot or pan" , "A tool for household use" , "Tool for practical use" .)