Clip of two reserves - one after another - making a mistake (6)

'a mistake' is the definition.
(informal term for a mistake)

'clip of two reserves one after' is the wordplay.
'two reserves' can mean two replacements for 'reserve'.
'clip of' means to remove the last letter (clip can mean a shortening of something).
'reserve' becomes 'book' (to book something is to reserve it).
'reserve' becomes 'boo' (I can't explain this - if you can you should believe this answer much more).
'one after' means one lot of letters go next to another.
'book' with its final letter taken away is 'boo'.
'boo'+'boo'='BOOBOO'

'another making' is the link.
This may not be right. Some or all of it may belong to another bit of the clue.

Can you help me to learn more?