Doctor interrupted by peculiar surly type (5)
I believe the answer is:
grump
'surly type' is the definition.
(I've seen this before)
'doctor interrupted by peculiar' is the wordplay.
'doctor' becomes 'gp' (general practitioner).
'interrupted by' means one lot of letters goes inside another.
'peculiar' becomes 'rum' (synonyms).
'gp' placed around 'rum' is 'GRUMP'.
(Other definitions for grump that I've seen before include "Sulky type" , "Crosspatch" , "surly type" , "Surly person" , "Sulky person" .)