Campsite shelter for some forgotten troop (4)
I believe the answer is:
tent
'campsite shelter' is the definition.
(I've seen this in another clue)
'some forgotten troop' is the wordplay.
'some' says the answer is hidden in the clue (some parts of the word are used).
'TENT' is hidden within 'forgotten troop'.
'for' is the link.
(Other definitions for tent that I've seen before include "Cloth shelter" , "Guy" , "some guys held on to?" , "Portable shelter for camper" , "Bivvy" .)