Panic seen in Territorial Army (5)
I believe the answer is:
alarm
'panic' is the definition.
(I've seen this before)
'in territorial army' is the wordplay.
'in' says the answer is hidden in the clue.
'ALARM' is hidden within 'territorial army'.
'seen' is the link.
(Other definitions for alarm that I've seen before include "Fright" , "Tocsin" , "Safety bell or alert signal" , "Unnerve" , "Warning siren" .)