Fool in Conservative crowd (4)
I believe the answer is:
clot
'fool' is the definition.
(I've seen this in other clues)
'conservative crowd' is the wordplay.
'conservative' becomes 'C' (UK political abbreviation).
'crowd' becomes 'lot' (a lot of people).
'c'+'lot'='CLOT'
'in' is the link.
(Other definitions for clot that I've seen before include "Mass of material" , "Thrombus - fool" , "Coagulate -- 1 across person" , "Thick lump - thick person" , "Silly billy" .)