Disorderly nit, impolite to enter uninvited (7)
I believe the answer is:
intrude
'enter uninvited' is the definition.
(I've seen this before)
'disorderly nit impolite' is the wordplay.
'disorderly' indicates an anagram.
'impolite' becomes 'rude' ('rude' can be similar in meaning to 'impolite').
'nit' with letters rearranged gives 'int'.
'int'+'rude'='INTRUDE'
'to' acts as a link.
(Other definitions for intrude that I've seen before include "Push in uninvited" , "Untried (anag)" , "Join in without being invited or wanted" , "Trespass" , "Gatecrash" .)