The old man meeting the devil, said to bring terror (5)
I believe the answer is:
panic
'terror' is the definition.
('panic' can be a synonym of 'terror')
'the old man meeting the devil said' is the wordplay.
'the old man' becomes 'pa' ('pa' can be a synonym of 'old man').
'meeting' is a charade indicator (letters next to each other).
'the devil' becomes 'nick' (Nick and Old Nick are names for the Devil).
'said' indicates a 'sounds like' (homophone) clue.
'nick' is a homophone of 'nic'.
'pa'+'nic'='PANIC'
'to bring' is the link.
(Other definitions for panic that I've seen before include "Losing one's head" , "Lose one's cool" , "Lose one's nerve" , "Take fright, lose the head" , "Alarm - terror" .)