Alerted to crashing bore (9)
I believe the answer is:
tolerated
'bore' is the definition.
('tolerate' can be a synonym of 'bear')
'alerted to crashing' is the wordplay.
'crashing' indicates anagramming the letters.
'alerted'+'to'='alertedto'
'alertedto' is an anagram of 'TOLERATED'.
(Other definitions for tolerated that I've seen before include "accepted?" , "Borne" , "Endured; allowed" , "Bore" , "Put up with" .)