American doctor in excursion to find instrument (7)
I believe the answer is:
tambour
'instrument' is the definition.
(tambour is a kind of instrument)
'american doctor in excursion' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'doctor' becomes 'mb' (Bachelor of Medicine, Medicinae Baccalaureus).
'in' indicates putting letters inside.
'excursion' becomes 'tour' (I've seen this before).
'a'+'mb'='amb'
'amb' going into 'tour' is 'TAMBOUR'.
'to find' is the link.
(Other definitions for tambour that I've seen before include "construction of sewers" , "feature of some courts" , "Drum or embroidery frame" , "circle for 13 [NEEDLEWORK]" , "Beat this" .)