Seize and take into custody (6)
I believe the answer is:
arrest
'seize and take into custody' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for arrest that I've seen before include "Detain under suspicion of criminal behaviour" , "Land next to the sea" , "Seize and take into custody" , "Sartre (anag) -- check" , "Apprehend; detain" .)