Spook found the sources of leaks easily (7)
I believe the answer is:
startle
'spook' is the definition.
(I've seen this in another clue)
'found the sources of leaks easily' is the wordplay.
'found' becomes 'start' (as in to establish).
'the sources of' suggests taking the first letters (the beginning of a word is its sauce).
The initial letters of 'leaks easily' is 'le'.
'start'+'le'='STARTLE'
(Other definitions for startle that I've seen before include "Take by surprise" , "Take unawares with rattles" , "Shock, alarm" , "Take (someone) aback" , "Cause shock to" .)