A charmingly old-fashioned Conservative's brought in to advise (8)
I believe the answer is:
acquaint
'advise' is the definition.
(thesaurus)
'a charmingly old-fashioned conservative's brought in' is the wordplay.
'charmingly old-fashioned' becomes 'quaint' (I've seen this before).
'conservative' becomes 'c' (abbreviation commonly used in UK politics).
'brought in' means one lot of letters goes inside another.
'a'+'quaint'='aquaint'
'aquaint' placed around 'c' is 'ACQUAINT'.
'to' acts as a link.
(Other definitions for acquaint that I've seen before include "Make aware or familiar with, say the facts" , "Make someone familiar with" , "get up to date" , "brief" , "Get to come to know" .)