Separate in Calcutta (3)
I believe the answer is:
cut
'separate' is the definition.
(cutting is a kind of separating)
'in calcutta' is the wordplay.
'in' says the answer is hidden in the clue.
'CUT' is hidden within 'calcutta'.
(Other definitions for cut that I've seen before include "Cold-shoulder" , "Slice, chop" , "Sever - hurt - snub" , "Abbreviate" , "Slight" .)