Shark that's more confident behind you (6)
I believe the answer is:
usurer
'shark' is the definition.
(I know that usurer is a type of shark)
'more confident behind you' is the wordplay.
'more confident' becomes 'surer' ('sure' can be similar in meaning to 'confident').
'behind' is a charade indicator (letters next to each other).
'you' becomes 'u' (commonly used in online communication).
'surer' after 'u' is 'USURER'.
'that's' acts as a link.
(Other definitions for usurer that I've seen before include "loan-shark" , "Unfair moneylender" , "Businessman taking a lot of interest" , "Person who charges excessive interest on loan" , "Unscrupulous lender" .)