Madness to steal second! Madness! (8)
I believe the answer is:
insanity
'madness' is the definition.
(I know that madness can be written as insanity)
'steal second madness' is the wordplay.
I cannot really understand how this works, but
'second' could be 's' (common abbreviation) and 's' is located in the answer.
The remaining letters 'inanity' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
'to' acts as a link.
Can you help me to learn more?
(Other definitions for insanity that I've seen before include "Mental derangement" , "folly" , "Lunacy, derangement" , "Lunacy, madness" , "mania" .)