The penniless have nothing (3)
I believe the answer is:
nil
'nothing' is the definition.
(eg nil is zero in football)
'the penniless have' is the wordplay.
'have' says the answer is hidden in the clue.
'NIL' is hidden in the letters of 'penniless'.
(Other definitions for nil that I've seen before include "0" , "Love" , "Nothing, no value" , "Nothing found in senility" , "Nothing, naught" .)