Regarded as seven minus five (4)
I believe the answer is:
seen
'regarded' is the definition.
'seven minus five' is the wordplay.
'minus' indicates named letters should be taken away.
'five' becomes 'v' ('V' can be a synonym of 'five').
'seven' with 'v' removed is 'SEEN'.
'as' acts as a link.
(Other definitions for seen that I've seen before include "Perceived by sight" , "Viewed" , "watched" , "Met - understood" , "Observed or percieved" .)