I had nothing left to worship (4)
I believe the answer is:
idol
'worship' is the definition.
(idol worship is a kind of worship)
'i had nothing left' is the wordplay.
'i had' becomes 'id' (I'd).
'nothing' becomes 'o' (looks like zero - 0).
'left' becomes 'l' (common abbreviation).
'id'+'o'+'l'='IDOL'
'to' is the link.
(Other definitions for idol that I've seen before include "Effigy" , "Heathen god" , "Much-loved actor" , "Images of devotion" , "Graven image (sometimes false?)" .)