To write at half pace brings little money (5)
I believe the answer is:
pence
'little money' is the definition.
(I've seen this before)
'to write at half pace' is the wordplay.
'to write' becomes 'pen' ('pen' can be a synonym of 'write').
'at' says to put letters next to each other.
'half' indicates taking half.
'pace' with half the letters taken is 'ce'.
'pen'+'ce'='PENCE'
'brings' acts as a link.
(Other definitions for pence that I've seen before include "British coins" , "President's vice" , "Little coins" , "Small-value coins" , "Lowest denomination of British currency" .)