Are sure to be in trouble during army detention (5,6)
I believe the answer is:
house arrest
'detention' is the definition.
(house arrest is a kind of detention)
'are sure to be in trouble during army' is the wordplay.
'to be in trouble' indicates an anagram.
'during' means one lot of letters goes inside another.
'army' becomes 'host' (host is a kind of army).
'are'+'sure'='aresure'
'aresure' is an anagram of 'usearre'.
'usearre' placed into 'host' is 'HOUSE-ARREST'.
(Other definitions for house arrest that I've seen before include "Confinement to one's own home" , "kept at home" , "Domestic restriction" , "detention" .)