Support is not commonly accepted by person one’s interrupted (8)
I believe the answer is:
maintain
'support' is the definition.
(I've seen this before)
'not commonly accepted by person one's interrupted' is the wordplay.
'not commonly' becomes 'aint' (non-standard version of 'isn't' or 'aren't').
'accepted by' indicates putting letters inside (inserted letters are accepted).
'person' becomes 'man' (man is a kind of person).
'one' becomes 'i' (Roman numeral).
'interrupted' means one lot of letters goes inside another.
'man' going around 'i' is 'main'.
'aint' placed into 'main' is 'MAINTAIN'.
'is' is the link.
(Other definitions for maintain that I've seen before include "Preserve or contend" , "Keep - support" , "Keep in good order" , "Keep in a certain state" , "Keep going" .)