Encroach during tango, lacking good manners (7)
I believe the answer is:
intrude
'encroach' is the definition.
(I've seen this before)
'during tango lacking good manners' is the wordplay.
'during' becomes 'in' (e.g. during February means in February).
'tango' becomes 'T' (phonetic alphabet: alpha, bravo, charlie etc.).
'lacking good manners' becomes 'rude' (rudeness is a lack of manners).
'in'+'t'+'rude'='INTRUDE'
(Other definitions for intrude that I've seen before include "Push in uninvited" , "Break in" , "Encroach on others' privacy" , "Pry" , "Push in where not wanted" .)