Wrong girl, for a start (5)
I believe the answer is:
amiss
'wrong' is the definition.
(I know that wrong can be written as amiss)
'girl for a start' is the wordplay.
'girl' becomes 'iss' (I can't justify this - if you can you should give a lot more credence to this answer).
'for' is a charade indicator (letters next to each other) (I've seen this in other clues).
'a' becomes 'amp' (A is the symbol for the amp or ampere).
'start' means to remove the last letter (I've seen 'starts' mean this).
'amp' with its final letter removed is 'am'.
'iss' put after 'am' is 'AMISS'.
Can you help me to learn more?
(Other definitions for amiss that I've seen before include "Badly - wrong" , "In an inappropriate way" , "Not functioning properly" , "Wrorg" , "(Gone) wrong" .)