Role in clinic is plain (7)
I believe the answer is:
spartan
'is plain' is the definition.
(I've seen this before)
'role in clinic' is the wordplay.
'role' becomes 'part' (eg a part or role in a film).
'in' is an insertion indicator.
'clinic' becomes 'san' (short for sanatorium).
'part' put inside 'san' is 'SPARTAN'.
(Other definitions for spartan that I've seen before include "Basic" , "Austere - like Lysander?" , "Austere, lacking comfort" , "Severe" , "Lacking comfort or luxury" .)