Sort of hut in Tunis sentries use (6)
I believe the answer is:
nissen
'sort of hut' is the definition.
(I've seen this before)
'in tunis sentries use' is the wordplay.
'in' indicates the answer is hidden within the clue.
'NISSEN' can be found hidden inside 'tunis sentries use'.
(Other definitions for nissen that I've seen before include "Designer of corrugated iron huts" , "Wartime hut" , "Othello's lieutenant" , "Designer of type of corrugated iron hut" , "Prefab hut designer" .)