Church leader perturbed at first about petty quarrel (7)
I believe the answer is:
pontiff
'church leader' is the definition.
'pontiff' can be an answer for 'leader' (pontiff is a kind of leader). I am not certain of the 'church' bit.
'perturbed at first about petty quarrel' is the wordplay.
'at first' suggests taking the first letters.
'about' becomes 'on' (as in a book 'on' a certain topic).
'petty quarrel' becomes 'tiff' (I've seen this before).
The first letter of 'perturbed' is 'p'.
'p'+'on'+'tiff'='PONTIFF'
Can you help me to learn more?
(Other definitions for pontiff that I've seen before include "Bishop" , "Religious leader" , "High-priest" , "Head of the Roman Catholic church" , "Title for a pope" .)