Unwise message to a girl, for money (5)
I believe the answer is:
dimes
'unwise message to a girl for money' is the definition.
I can't judge whether this defines the answer.
'message to a girl for money' is the wordplay.
'message' becomes 'es' (I can't justify this - if you can you should believe this answer much more).
'to a' is a charade indicator (letters next to each other) (I've seen this in other clues).
'girl' becomes 'di'.
'for' means one lot of letters go next to another.
'money' becomes 'm' (abbreviation used in economics).
'di'+'m'='dim'
'es' after 'dim' is 'DIMES'.
Can you help me to learn more?
(Other definitions for dimes that I've seen before include "Tenths of a dollar" , "$0.10n (n>1)" , "US ten-cent coins" , "Ten-cent coins of USA" , "Tenths of dollars" .)