Capable of an outburst? (3)
I believe the answer is:
fit
This clue is a double definition.
'capable' is the first definition.
(thesaurus)
'an outburst?' is the second definition.
(I know that fit can be written as fit)
'of' acts as a link.
(Other definitions for fit that I've seen before include "Appropriate -- not 21" , "Suitable; sudden attack" , "Adapt; well" , "Sound in body or suitable" , "Apt" .)