Dad with English church leader (4)
I believe the answer is:
pope
'church leader' is the definition.
(I've seen this before)
'dad with english' is the wordplay.
'dad' becomes 'pop' (synonyms).
'with' means one lot of letters go next to another.
'english' becomes 'e' (abbreviation).
'pop'+'e'='POPE'
(Other definitions for pope that I've seen before include "served in the Vatican" , "church leader in Rome" , "Catholic leader" , "author" , "Head of RC church" .)