Partly declaim, partly communicate (6)
I believe the answer is:
impart
'communicate' is the definition.
(imparting is a kind of communicating)
'partly declaim partly' is the wordplay.
'partly' indicates a hidden word.
'IMPART' is hidden within 'declaim partly'.
(Other definitions for impart that I've seen before include "Convey information, make known" , "Tell, pass on" , "Divulge, make known" , "Communicate (information)" , "Give - tell" .)