Old conquerors — and not belonging to island (7)
I believe the answer is:
normans
'old conquerors' is the definition.
'normans' can be an answer for 'conquerors' (I've seen this before). I'm not sure about the 'old' bit.
'and not belonging to island' is the wordplay.
'and not' becomes 'nor' ('nor' means 'and also not').
'belonging' becomes 's' (I am not sure about this - if you are sure you should believe this answer much more).
'to' says to put letters next to each other (I've seen this in other clues).
'island' becomes 'Man' (the Isle of Man is an example).
's' put after 'man' is 'mans'.
'nor'+'mans'='NORMANS'
Can you help me to learn more?
(Other definitions for normans that I've seen before include "belonging to Greg the golfer?" , "Some Frenchmen" , "Our last successful invaders" , "They won the battle of Hastings" , "Invaders in 1066" .)