A case of Honolulu beyond old Hawaiian island (4)
I believe the answer is:
oahu
'hawaiian island' is the definition.
(I've seen this before)
'a case of honolulu beyond old' is the wordplay.
'case of' means to remove the middle letters (outsides of).
'beyond' means one lot of letters go next to another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'honolulu' with its middle taken out is 'hu'.
'a'+'hu'='ahu'
'ahu' after 'o' is 'OAHU'.
(Other definitions for oahu that I've seen before include "popular Pacific location" , "Honolulu's island" , "Chief island of Hawaii" , "Hawaiian island" , "Pacific island" .)