Section of text Rattigan found to be superfluous (5)
I believe the answer is:
extra
'be superfluous' is the definition.
('extra' can be a synonym of 'superfluous')
'section of text rattigan found' is the wordplay.
'section of' says the answer is hidden in the clue.
'EXTRA' is hidden within 'text rattigan found'.
'to' acts as a link.
(Other definitions for extra that I've seen before include "Additional or supplementary" , "Player taking little part" , "Supplemental" , "Additional - run - actor - newspaper edition" , "Additional - bye" .)