There's only me to depend on (6)
I believe the answer is:
merely
'there's only' is the definition.
I can't tell whether this defines the answer.
'me to depend on' is the wordplay.
'to depend' becomes 'rely' (to depend on someone is to rely on them).
'on' is a charade indicator (letters next to each other).
'me'+'rely'='MERELY'
Can you help me to learn more?
(Other definitions for merely that I've seen before include "Simply - only" , "Just one" , "'Only, and nothing more (6)'" .)