High priest in Heligoland (3)
I believe the answer is:
eli
'high priest' is the definition.
(biblical figure)
'in heligoland' is the wordplay.
'in' indicates the answer is hidden within the clue.
'ELI' is hidden in the letters of 'heligoland'.
(Other definitions for eli that I've seen before include "Priest at Shiloh (Samuel)" , "Biblical high priest" , "patriarch" , "- Whitney invented the cotton gin in seventeen ninety three" , "High priest in the Book of Samuel" .)