Didn't match when she was dressed in to go out (7)
I believe the answer is:
clashed
'out' is the definition.
The answer and definition are not the same part of speech. However, past participle verbs and adjectives sometimes define each other.
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for clashed that I've seen before include "Was incompatible" , "Came into conflict" .)