Dressed as one did first thing this morning (3,2)
I believe the answer is:
got up
'dressed' is the definition.
(getting up is a kind of dressing)
'one did first thing this morning' is the wordplay.
I cannot really understand how this works, but
'first thing' could be 't' (1st letter of 'thing') and 't' is located in the answer.
The remaining letters 'goup' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
'as' acts as a link.
Can you help me to learn more?
(Other definitions for got up that I've seen before include "20 [ROSE]" , "Arose" , "made to look good?" , "Ascended" .)