Alarm found loud enough initially (7)
I believe the answer is:
startle
'alarm' is the definition.
(I've seen this before)
'found loud enough initially' is the wordplay.
'found' becomes 'start' (as in to establish).
'initially' suggests taking the first letters.
The initial letters of 'loud enough' is 'le'.
'start'+'le'='STARTLE'
(Other definitions for startle that I've seen before include "Make jump" , "Take unawares with rattles" , "Alarm suddenly" , "Surprise with starlet" , "Astonish" .)