Isle of Wight is supported by an American (5)
I believe the answer is:
iowan
'american' is the definition.
(someone from Iowa)
'isle of wight is supported by an' is the wordplay.
'isle of wight' becomes 'iow' (this could be a standard abbreviation I've not previously seen).
'is supported by' is a charade indicator (letters next to each other) (in a down clue, some letters hold up others).
'iow'+'an'='IOWAN'
Can you help me to learn more?
(Other definitions for iowan that I've seen before include "Midwesterner" , "Statesman" , "American" , "One from Des Moines perhaps" , "From one US state" .)