Emperor and head of state welcomed by sailor (4)
I believe the answer is:
tsar
'emperor' is the definition.
(I've seen this before)
'head of state welcomed by sailor' is the wordplay.
'head of' suggests taking the first letters.
'welcomed by' means one lot of letters goes inside another (I've seen this in other clues).
'sailor' becomes 'tar' (tar is a kind of sailor).
The initial letter of 'state' is 's'.
's' going within 'tar' is 'TSAR'.
'and' acts as a link.
(Other definitions for tsar that I've seen before include "Despot" , "specific authority" , "Old Russian ruler" , "Old Russian 22" , "Eg, Ivan the Terrible" .)