No sailor alights on isle (8)
I believe the answer is:
landsman
'no sailor' is the definition.
(I've seen this before)
'alights on isle' is the wordplay.
'alights' becomes 'lands' (I've seen this before).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'isle' becomes 'man' (the Isle of Man is an example).
'lands'+'man'='LANDSMAN'
(Other definitions for landsman that I've seen before include "What the sailor calls the man ashore" , "not a seafaring type" .)