Duke only turning up in Greek island (5)
I believe the answer is:
delos
'greek island' is the definition.
(I've seen this before)
'duke only turning up' is the wordplay.
'duke' becomes 'd' (abbreviation).
'only' becomes 'sole' (synonyms).
'turning up' is a reversal indicator.
'sole' back-to-front is 'elos'.
'd'+'elos'='DELOS'
'in' acts as a link.
(Other definitions for delos that I've seen before include "Greek island, supposed birthplace of Apollo" , "Island of the Cyclades" , "Apollo's birthplace" .)