Thus, having to lubricate round sign (7)

'thus having to lubricate' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.

'round sign' is the wordplay.
I cannot quite understand how this works, but
'round' could be 'o' (round can mean a round object) and 'o' is found in the answer.
'sign' could be 'he' (he is a kind of sign) and 'he' is located in the answer.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?