Elected head of trustees, impolite to butt in (7)
I believe the answer is:
intrude
'butt in' is the definition.
(thesaurus)
'elected head of trustees impolite' is the wordplay.
'elected' becomes 'in'.
'head of' says to take the initial letters.
'impolite' becomes 'rude' ('rude' can be similar in meaning to 'impolite').
The initial letter of 'trustees' is 't'.
'in'+'t'+'rude'='INTRUDE'
'to' acts as a link.
(Other definitions for intrude that I've seen before include "Push in uninvited" , "Come in uninvited" , "Push in unwantedly" , "Butt in, interfere" , "Encroach on others' privacy" .)