Computer device doctor has to operate (5)
I believe the answer is:
mouse
'computer device' is the definition.
(I've seen this before)
'doctor has to operate' is the wordplay.
'doctor' becomes 'mo' (medical officer**).
'has' is a charade indicator (letters next to each other).
'to operate' becomes 'use' (I've seen this before).
'mo'+'use'='MOUSE'
(Other definitions for mouse that I've seen before include "Small rodent - computer device" , "Wimp" , "shy and timid type" , "computer operator" , "black eye" .)