What may be nuclear force covers a great distance to protect island (8)
I believe the answer is:
families
'what may be nuclear' is the definition.
I can't judge whether this defines the answer.
'force covers a great distance to protect island' is the wordplay.
'covers' says to take the initial letters (I've seen 'cover' mean this (in a down clue, the letter covering the word)).
'great distance' becomes 'miles' (I've seen this in another clue. I am not sure about the 'great' bit.).
'to protect' indicates putting letters inside (inserted letters are held or protected).
'island' becomes 'i' (geographical abbreviation).
The initial letter of 'force' is 'f'.
'miles' enclosing 'i' is 'milies'.
'f'+'a'+'milies'='FAMILIES'
Can you help me to learn more?
(Other definitions for families that I've seen before include "Parents and their children - lots of them" , "Groups related to one another by blood or marriage" , "Primary social groups" , "File Siam wrongly under social units" , "Kinship groups" .)