Suppose there's nothing to long for (5)
I believe the answer is:
opine
'suppose' is the definition.
(I know that suppose can be written as opine)
'nothing to long for' is the wordplay.
I cannot really understand how this works, but
'nothing' could be 'o' (O resembles 0) and 'o' is present in the answer.
'long' could be 'pine' (to pine for someone is to long for them) and 'pine' is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
'there's' acts as a link.
Can you help me to learn more?
(Other definitions for opine that I've seen before include "Consider" , "State as one's belief" , "Express a point of view" , "Express or hold view" , "State one's held view" .)