Party workers holding Democrat in custody (5)
I believe the answer is:
cadre
'party workers' is the definition.
'cadre' can be an answer for 'party' (thesaurus). I'm unsure of the 'workers' bit.
'democrat in custody' is the wordplay.
'democrat' becomes 'd'.
'in' means one lot of letters goes inside another.
'custody' becomes 'care' (I've seen this before).
'd' going inside 'care' is 'CADRE'.
'holding' is the link.
Can you help me to learn more?
(Other definitions for cadre that I've seen before include "Raced around the framework of a military unit" , "Raced around with army unit" , "Raced around with basic military unit" , "Fighting unit" , "Raced (anag) - small central group" .)