Girl upsets a clergyman (4)
I believe the answer is:
vera
'girl' is the definition.
'upsets a clergyman' is the wordplay.
'upsets' says the letters should be written backwards.
'clergyman' becomes 'rev' (short for reverend).
'a'+'rev'='arev'
'arev' back-to-front is 'VERA'.
(Other definitions for vera that I've seen before include "Duckworth, Lynn" , "Girl's name (meaning faith or true)" , "Woman's name" , "A girl to rave about" , ".. Lynn, aloe ..." .)