Ordinal carried by clergyman, in theory (5)
I believe the answer is:
ninth
'ordinal' is the definition.
(similar in meaning)
'carried by clergyman in theory' is the wordplay.
'carried by' indicates the answer is hidden within the clue.
'NINTH' is hidden within 'clergyman in theory'.
(Other definitions for ninth that I've seen before include "Third of a third" , "Beethoven's last?" , "Last of course to go out" , "interval" , "Eg, Beethoven's choral symphony" .)