Hamlet for one, feeble guy initially that’s not taken seriously (9)
I believe the answer is:
plaything
'that's not taken seriously' is the definition.
'hamlet for one feeble guy initially' is the wordplay.
'hamlet for one' becomes 'play'.
'feeble' becomes 'thin'.
'initially' says to take the initial letters.
The initial letter of 'guy' is 'g'.
'play'+'thin'+'g'='PLAYTHING'
(Other definitions for plaything that I've seen before include "someone treated lightly" , "used to impact king's conscience?" , "source of amusement" , "Toy" .)