Secret deliveries accepted by court (6)
I believe the answer is:
covert
'secret' is the definition.
('covert' can be similar in meaning to 'secret')
'deliveries accepted by court' is the wordplay.
'deliveries' becomes 'over' (I've seen this before).
'accepted by' indicates putting letters inside.
'court' becomes 'ct'.
'over' put inside 'ct' is 'COVERT'.
(Other definitions for covert that I've seen before include "Concealed, secret" , "Undercover; thicket" , "18 [HIDDEN]" , "Concealed like fox's liar" , "Thicket; not displayed" .)