Got into English poet, foremost of Dadaists (6)
I believe the answer is:
donned
'got into' is the definition.
('don' can be a synonym of 'get into')
'english poet foremost of dadaists' is the wordplay.
'english poet' becomes 'donne' (I've seen this before).
'foremost of' indicates taking the first letters.
The first letter of 'dadaists' is 'd'.
'donne'+'d'='DONNED'
(Other definitions for donned that I've seen before include "Put on, hat or coat" , "Put on, as with garment" , "Put on to wear" , "Put on (clothing)" , "Put on, appearance or clothes" .)