Noticed to be seven minus five (4)
I believe the answer is:
seen
'noticed' is the definition.
(I've seen this before)
'seven minus five' is the wordplay.
'minus' suggests deleting specific letters.
'five' becomes 'v' (roman numeral).
'seven' with 'v' taken out is 'SEEN'.
'to be' acts as a link.
(Other definitions for seen that I've seen before include "Spotted" , "Viewed" , "Sighted" , "Espied" , "watched" .)