Announce cramp oil treatment (8)
I believe the answer is:
proclaim
'announce' is the definition.
(I've seen this before)
'cramp oil treatment' is the wordplay.
'treatment' indicates an anagram (letters treated or processed differently).
'cramp'+'oil'='crampoil'
'crampoil' is an anagram of 'PROCLAIM'.
(Other definitions for proclaim that I've seen before include "Reveal" , "shout from the housetops" , "Broadcast" , "advertise" , "Announce officially or declare publicly" .)