Brackets getting equal space on treatises (11)
I believe the answer is:
parentheses
'brackets' is the definition.
(I've seen this before)
'equal space on treatises' is the wordplay.
'equal' becomes 'par'.
'space' becomes 'en' (in printing, a space as wide as a letter 'n').
'on' says to put letters next to each other.
'treatises' becomes 'theses' (thesis is a kind of treatise).
'par'+'en'+'theses'='PARENTHESES'
'getting' is the link.
(Other definitions for parentheses that I've seen before include "(shown here)" , "Round brackets" .)