Little backing of one busy in intelligence (3,3)

'little' is the definition.
(a wee bit can mean a little to a little extent)

'backing of one busy in intelligence' is the wordplay.
'backing of' says the letters should be written in reverse.
'one busy' becomes 'bee' (as in the phrase 'busy as a bee').
'in' indicates putting letters inside.
'intelligence' becomes 'wit' (wit is a kind of intelligence).
'bee' reversed gives 'eeb'.
'eeb' put inside 'wit' is 'WEE BIT'.