Responded, involving swan and deer (8)
I believe the answer is:
answered
'responded' is the definition.
('answer' can be a synonym of 'respond')
'involving swan and deer' is the wordplay.
'involving' is an anagram indicator.
'and' says to put letters next to each other.
'swan' put after 'deer' is 'deerswan'.
'deerswan' is an anagram of 'ANSWERED'.
(Other definitions for answered that I've seen before include "succeeded" , "was sufficient" , "Satisfied" , "Rejoined" , "Returned" .)