Unruly lads in Sicily, for instance (6)
I believe the answer is:
island
'sicily for instance' is the definition.
(I know that Sicilia is a island)
'unruly lads in' is the wordplay.
'unruly' is an anagram indicator.
'lads'+'in'='ladsin'
'ladsin' is an anagram of 'ISLAND'.
(Other definitions for island that I've seen before include "Refuge as in middle of road" , "Boffin, Baffin or Bali, say" , "eg Man, Wight" , "Man, say" , "Area in the main" .)