Criminal gang sending missile back over island (5)
I believe the answer is:
triad
'criminal gang' is the definition.
(I've seen this before)
'missile back over island' is the wordplay.
'missile' becomes 'dart' (Backwards).
'back' says the letters should be written in reverse.
'over' means one lot of letters goes inside another.
'island' becomes 'i' (geographical abbreviation).
'dart' reversed gives 'trad'.
'trad' enclosing 'i' is 'TRIAD'.
'sending' acts as a link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for triad that I've seen before include "Chinese criminal society" , "Could be major" , "three making a sound?" , "Union of three" , "trio" .)