Talk is no good in oil production! (5)
I believe the answer is:
lingo
'talk' is the definition.
(thesaurus)
'no good in oil production' is the wordplay.
'no good' becomes 'ng' (abbreviation).
'in' means one lot of letters goes inside another.
'production' indicates an anagram.
'oil' is an anagram of 'lio'.
'ng' going inside 'lio' is 'LINGO'.
'is' acts as a link.
(Other definitions for lingo that I've seen before include "Language (slang)" , "Log in (anag.)" , "means to communicate" , "Specialised vocabulary" , "Language (informally)" .)