Darts player's place in Rochester (4)
I believe the answer is:
oche
'darts player's place' is the definition.
(line behind which dart players throw darts)
'in rochester' is the wordplay.
'in' indicates the answer is hidden within the clue.
'OCHE' is hidden within 'rochester'.
(Other definitions for oche that I've seen before include "Line of 25 [ARROEWS]" , "Line behind which darts players stand" , "Line not to be crossed" , "Line behind which an 11 player throws" , "Line where dart thrower stands" .)