Hide furtively (4)
I believe the answer is:
lurk
'hide furtively' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for lurk that I've seen before include "Read (but take no part in) online chat" , "keep low profile" , "View an online forum without contributing" , "Loiter with intent" , "Linger around furtively" .)