Appropriate to hold a Republican in isolation? (5)
I believe the answer is:
apart
'in isolation?' is the definition.
(I've seen this before)
'appropriate to hold a republican' is the wordplay.
'appropriate' becomes 'apt' (synonyms).
'to hold' indicates putting letters inside.
'republican' becomes 'R' (abbreviation).
'a'+'r'='ar'
'apt' going around 'ar' is 'APART'.
(Other definitions for apart that I've seen before include "Divided" , "No longer living together" , "set aside" , "Separately, aside" , "Asunder" .)