In the morning, doctor finds shells (4)
I believe the answer is:
ammo
'shells' is the definition.
(I've seen this before)
'in the morning doctor' is the wordplay.
'in the morning' becomes 'am' (AM on a clock).
'doctor' becomes 'mo' (medical officer).
'am'+'mo'='AMMO'
'finds' is the link.
(Other definitions for ammo that I've seen before include "Bullets, etc. (colloq.)" , "that goes in magazine: ...?" , "Bullets (sl.)" , "What's fired from guns (abbr)" , "Contents of magazine" .)