Figure of Conservative earlier in retreat (7)
I believe the answer is:
decagon
'figure' is the definition.
(I've seen this before)
'conservative earlier in retreat' is the wordplay.
'conservative' becomes 'c' (abbreviation commonly used in UK politics).
'earlier' becomes 'ago' (I've seen this before).
'in' is an insertion indicator.
'retreat' becomes 'den'.
'c'+'ago'='cago'
'cago' put inside 'den' is 'DECAGON'.
'of' acts as a link.
(Other definitions for decagon that I've seen before include "Ten-sided plane figure" , "Ten-sided shape" , "Plane shape" , "10-sided figure" , "Go, dance on geometric figure with ten sides" .)