Takes off bloomers, having posed at the outset (9)
I believe the answer is:
satirises
'takes off' is the definition.
(take off can mean to mock or satirise)
'bloomers having posed at the outset' is the wordplay.
I cannot quite see how this works, but
'bloomers' could be 'irises' and 'irises' is found within the answer.
'posed' could be 'sat' (posed or sat for an artist) and 'sat' is found within the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for satirises that I've seen before include "Makes exaggerated attacks" , "Makes fun of" , "Sends up" , "Ridicules" .)