Write about English coins (5)
I believe the answer is:
pence
'coins' is the definition.
(penny is a kind of coin)
'write about english' is the wordplay.
'write' becomes 'pen' (synonyms).
'about' becomes 'c' (abbreviation for 'circa').
'english' becomes 'E' (abbreviation).
'pen'+'c'+'e'='PENCE'
(Other definitions for pence that I've seen before include "little money" , "Fractions of a pound" , "Little coins" , "President's vice" , "p" .)