The quiet type with nothing to ponder about (5)
I believe the answer is:
mouse
'the quiet type' is the definition.
(I've seen this before)
'nothing to ponder about' is the wordplay.
'nothing' becomes 'O' (looks like zero - 0).
'to ponder' becomes 'muse' (synonyms).
'about' indicates putting letters inside.
'o' going into 'muse' is 'MOUSE'.
'with' acts as a link.
(Other definitions for mouse that I've seen before include "Small creature" , "Cursor control" , "Domestic rodent" , "control of computer system" , "Tiny creature" .)