Perplexed American playwright needing surprise ultimately in plot (10)
I believe the answer is:
bewildered
'perplexed' is the definition.
('bewilder' can be a synonym of 'perplex')
'american playwright needing surprise ultimately in plot' is the wordplay.
'american playwright' becomes 'wilder' (I can't justify this - if you can you should give a lot more credence to this answer).
'needing' says to put letters next to each other.
'ultimately' indicates one should take the final letters.
'in' is an insertion indicator.
'plot' becomes 'bed' (a plot of land).
The final letter of 'surprise' is 'e'.
'wilder' put after 'e' is 'ewilder'.
'ewilder' put within 'bed' is 'BEWILDERED'.
Can you help me to learn more?
(Other definitions for bewildered that I've seen before include "Surprised" , "appearing clueless" , "Baffled" , "At a loss!" , "Confused" .)