Fearful of such a breakdown (7)
I believe the answer is:
nervous
I believe this is a double definition.
'fearful' is the first definition.
(I've seen this before)
'such a breakdown' is the second definition.
(nervous breakdown is a kind of breakdown)
'of' acts as a link.
(Other definitions for nervous that I've seen before include "Twitchy" , "Worried, apprehensive" , "Easily alarmed" , "Anxious or apprehensive" , "On edge, anxious" .)