People under tree being church dignitaries (8)
I believe the answer is:
aldermen
'church dignitaries' is the definition.
'aldermen' can be an answer for 'dignitaries' (I have seen 'Civil dignitaries ' mean 'aldermen' so perhaps 'dignitaries' could also mean 'aldermen'). I am not sure about the 'church' bit.
'people under tree' is the wordplay.
'people' becomes 'men' (men are people).
'under' means one lot of letters go next to another.
'tree' becomes 'alder' (alder is a kind of tree).
'men' after 'alder' is 'ALDERMEN'.
'being' acts as a link.
Can you help me to learn more?
(Other definitions for aldermen that I've seen before include "Civil dignitaries" , "Civic dignitaries" , "former councillors" .)