I agree about returning thanks for poet (5)
I believe the answer is:
yeats
'poet' is the definition.
(Yeats is an example)
'i agree about returning thanks' is the wordplay.
'i agree' becomes 'yes' (I've seen this before).
'about' means one lot of letters goes inside another.
'returning' is a reversal indicator.
'thanks' becomes 'ta' (UK informal version of 'thank you').
'ta' written backwards gives 'at'.
'yes' going around 'at' is 'YEATS'.
'for' acts as a link.
(Other definitions for yeats that I've seen before include "W.B. - (Irish poet)" , "Irish poet, 1923 Nobel Prize winner" , "William Butler ....., poet and dramatist" , "William Butler ..., great Irish poet" , "William Butler .. . . ., Nobel-winning poet" .)