Specialist army unit brought back to protect English ruler overseas (5)
I believe the answer is:
emeer
'specialist' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe you can see an association between them that I don't see?
'army unit brought back to protect english ruler overseas' is the wordplay.
I cannot really see how this works, but
'unit' could be 'em' (em is a kind of unit) and 'em' is found in the answer.
'english' could be 'e' (abbreviation) and 'e' is located in the answer.
'ruler' could be 'er' (abbreviation for Elizabeth Regina) and 'er' is found in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for emeer that I've seen before include "Leader of Arabs" , "Arabic title" , "independent ruler" , "Islamic title" , "Prince" .)