Cleric who, being tense, gets nothing right! (6)
I believe the answer is:
pastor
'cleric' is the definition.
(thesaurus)
'being tense gets nothing right' is the wordplay.
'being tense' becomes 'past' (I've seen this in another clue).
'gets' says to put letters next to each other.
'nothing' becomes 'O' (looks like zero - 0).
'right' becomes 'r' (common abbreviation).
'past'+'o'+'r'='PASTOR'
'who' acts as a link.
(Other definitions for pastor that I've seen before include "A sport (anag)" , "One with a flock (of people)" , "Member of the clergy" , "Old shepherd" , "Minister of religion" .)