Settled, broken by pressure to reject strikes (4)
I believe the answer is:
taps
'strikes' is the definition.
(tapping is a kind of striking)
'settled broken by pressure to reject' is the wordplay.
'settled' becomes 'sat' (sat down).
'broken by' is an insertion indicator (inserted letters break into the word).
'pressure' becomes 'p' (abbreviation).
'to reject' shows that the letters should be reversed in order.
'sat' enclosing 'p' is 'spat'.
'spat' backwards is 'TAPS'.
(Other definitions for taps that I've seen before include "Military signal to turn the lights out" , "Bugs (wire)" , "Knocks gently" , "Military signal and faucets" , "Exploits" .)