Additional piece of text rarely seen (5)
I believe the answer is:
extra
'additional' is the definition.
(thesaurus)
'of text rarely seen' is the wordplay.
'of' indicates the answer is hidden within the clue.
'EXTRA' is hidden within 'text rarely seen'.
'piece' acts as a link.
(Other definitions for extra that I've seen before include "Maybe wide" , "23 player?" , "Superfluous" , "Possibly a bad ball" , "No great contribution to film" .)