Secure player in a pack (4)
I believe the answer is:
lock
I believe this clue is a double definition.
'secure' is the first definition.
(locking is a kind of securing)
'player in a pack' is the second definition.
(rugby)
(Other definitions for lock that I've seen before include "Stop moving" , "forward" , "A little hair" , "Security device - tuft of hair" , "Clasp" .)