Put off payment for Trident, supposedly (9)
I believe the answer is:
deterrent
'trident supposedly' is the definition.
I can't judge whether this defines the answer.
'put off payment' is the wordplay.
'put off' becomes 'deter' (both can mean to discourage).
'payment' becomes 'rent' (rent is a kind of payment).
'deter'+'rent'='DETERRENT'
'for' is the link.
Can you help me to learn more?
(Other definitions for deterrent that I've seen before include "Something discouraging action" , "It restrains" , "Nuclear weapons allegedly" , "Weapon to discourage attack" , "It acts to discourage" .)