An ill-considered breakout (4)
I believe the answer is:
rash
I believe this clue is a double definition.
'an ill-considered' is the first definition.
(I've seen this before)
'breakout' is the second definition.
(I've seen this in another clue)
(Other definitions for rash that I've seen before include "Hotheaded" , "Ill-advised" , "Harum-scarum" , "Incautious" , "Red patch on skin" .)