Arouse a section of the national army (5)
I believe the answer is:
alarm
'arouse' is the definition.
(I've seen this in another clue)
'a section of the national army' is the wordplay.
'a section of' indicates a hidden word.
'ALARM' can be found hidden inside 'national army'.
(Other definitions for alarm that I've seen before include "Warning sound or signal" , "Panicky concern" , "Warning bell" , "Panicky arousal" , "Scare with warning device" .)