Dodgily roped in to swallow hot new painkiller (9)
I believe the answer is:
endorphin
'painkiller' is the definition.
(I know that endorphin is a opioid)
'dodgily roped in to swallow hot new' is the wordplay.
I cannot quite see how this works, but
'in' is found in the answer.
'hot' could be 'h' (abbreviation eg on taps) and 'h' is located in the answer.
'new' could be 'n' (common abbreviation eg NT for New Testament) and 'n' is found within the answer.
an anagram of 'roped' is 'edorp' which is within the left over letters.
No letters remain.
This explanation may well be incorrect...
(Other definitions for endorphin that I've seen before include "painkiller" , "Hormone in the brain with an analgesic effect" , "Neurochemical with analgesic properties - dinner hop (anag)" , "Opiate-like substance produced in the brain" .)