Hilarious Conservative wearing weird hairstyle (10)
I believe the answer is:
hysterical
'hilarious' is the definition.
(thesaurus)
'conservative wearing weird hairstyle' is the wordplay.
'conservative' becomes 'c' (abbreviation commonly used in UK politics).
'wearing' indicates putting letters inside.
'weird' indicates an anagram.
'hairstyle' with letters rearranged gives 'hysterial'.
'c' going within 'hysterial' is 'HYSTERICAL'.
(Other definitions for hysterical that I've seen before include "overwrought" , "Emotionally unstable" , "Violently emotional" , "extraordinary" , "Extremely funny" .)