Language making a comeback in processional at a cathedral (7)
I believe the answer is:
catalan
'language' is the definition.
(Catalan is an example)
'a comeback in processional at a cathedral' is the wordplay.
'a comeback' says the letters should be written backwards.
'in' says the answer is hidden in the clue.
'nalatac' is hidden in the letters of 'processional at a cathedral'.
'nalatac' written backwards gives 'CATALAN'.
'making' is the link.
(Other definitions for catalan that I've seen before include "Language of NE Spain" , "Language spoken in Spain" , "Language of Spanish region" , "eg Carles Puigdemont" , "One from NE Spain" .)