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 a hidden word.
'OCHE' is hidden in the letters of '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" .)