New locum changed drug, accepted reluctantly (9)
I believe the answer is:
unwelcome
'accepted reluctantly' is the definition.
(people who are unwelcome are accepted reluctantly)
'new locum changed drug' is the wordplay.
'changed' is an anagram indicator.
'drug' becomes 'e' (e is another name for ecstasy).
'new'+'locum'='newlocum'
'newlocum' anagrammed gives 'unwelcom'.
'unwelcom'+'e'='UNWELCOME'
(Other definitions for unwelcome that I've seen before include "No received with pleasure - by host?" , "Bad (news); not acceptable" , "Not greeted or received with pleasure, quite the opposite" , "Not wanted" , "Not gladly received" .)