Viscount Greystoke spotted in Gibraltar and Zanzibar (6)
I believe the answer is:
tarzan
'viscount greystoke' is the definition.
(fictional character)
'in gibraltar and zanzibar' is the wordplay.
'in' indicates putting letters inside.
'gibraltar' becomes 'tara' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'and' becomes 'n' (common abbreviation for 'and').
'zanzibar' becomes 'z'.
'tara'+'n'='taran'
'taran' placed around 'z' is 'TARZAN'.
'spotted' is the link.
This may not be right. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for tarzan that I've seen before include "Hero of Edgar Rice Burroughs novels" , "Earl of Greystoke" , "E. R. Burroughs' hero" , "Edgar Rice Burroughs's man of the jungle" , "John Clayton, Lord Greystoke" .)