Enforcer-in-chief's right — extremist spilling his guts (8)
I believe the answer is:
martinet
'enforcer' is the definition.
(a martinet is a disciplinarian)
'in-chief's right extremist spilling his guts' is the wordplay.
'in' is an insertion indicator.
'chief' becomes 'main' (synonyms).
'right' becomes 'rt' (abbreviation as in Rt Hon- the Right Honourable).
'spilling his guts' means to remove the middle letters (the 'guts' of the word are removed).
'extremist' with its middle taken out is 'et'.
'main' going around 'rt' is 'martin'.
'martin'+'et'='MARTINET'
(Other definitions for martinet that I've seen before include "Rigorous figure" , "Strict disciplinarian - met train (anag)" , "drillmaster" , "Trite man becomes a tyrant" , "A rigorous operator" .)