Sailor collars second Russian boss (4)
I believe the answer is:
tsar
'russian boss' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'sailor collars second' is the wordplay.
'sailor' becomes 'tar' (slang term for a sailor).
'collars' is an insertion indicator (to collar can mean to apprehend or capture).
'second' becomes 's' (common abbreviation).
'tar' placed around 's' is 'TSAR'.
Can you help me to learn more?
(Other definitions for tsar that I've seen before include "Alexander and Nicholas held this title in Russia" , "Russian leader" , "Rats (anag)" , "Autocrat" , "specific authority" .)