Was a poser part of the weekend? (3)
I believe the answer is:
sat
'part of the weekend?' is the definition.
(abbreviation for Saturday)
'was a poser' is the wordplay.
I cannot quite understand how this works, but
'a' is found in the answer.
The remaining letters 'st' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for sat that I've seen before include "Used a chair" , "Took (an exam)" , "Took (examination)" , "Pulled up a 29 down" , "Relaxed" .)