Conservative support for revolutionary made CIA irrelevant (8)
I believe the answer is:
academic
'irrelevant' is the definition.
(I've seen this before)
'conservative support for revolutionary made cia' is the wordplay.
'conservative' becomes 'C' (UK political abbreviation).
'support for' says to put letters next to each other (in a down clue, some letters \'support\' others).
'revolutionary' indicates an anagram.
'made'+'cia'='madecia'
'madecia' with letters rearranged gives 'academi'.
'c' after 'academi' is 'ACADEMIC'.
(Other definitions for academic that I've seen before include "Unimportant" , "what's not relevant" , "Scholarly; irrelevant" , "Not expected to produce any practical result" , "Associated with places of higher learning" .)