Into the duck pate I put a sedative (6)
I believe the answer is:
opiate
'a sedative' is the definition.
(I've seen this before)
'into the duck pate i' is the wordplay.
'into' indicates putting letters inside.
'the duck' becomes 'o' (resembles zero - 'duck' in cricket).
'o'+'pate'='opate'
'opate' going around 'i' is 'OPIATE'.
'put' is the link.
(Other definitions for opiate that I've seen before include "Narcotic drug" , "description of religion?" , "Narcotic, such as morphine" , "Drug made from poppy" , "Type of drug" .)