Surrounded by some of the pyramids (4)
I believe the answer is:
amid
'surrounded by' is the definition.
(amid means among or surrounded by)
'some of the pyramids' is the wordplay.
'some of' indicates a hidden word.
'AMID' can be found hidden inside 'pyramids'.
(Other definitions for amid that I've seen before include "Surrounded by" , "In the centre of" , "'See . . . . the winter's snow' (carol)" , "A dim sort of preposition" , "Among" .)