Nothing like a century to reverse form (3,1,7)
I believe the answer is:
not a sausage
'nothing' is the definition.
('not a sausage' can informally mean nothing)
'a century to reverse form' is the wordplay.
'century' becomes 'ton' (both can mean one hundred of something).
'to reverse' is a reversal indicator.
'form' becomes 'sausage' (I can't justify this - if you can you should give a lot more credence to this answer).
'a'+'ton'='aton'
'aton' in reverse letter order is 'nota'.
'nota'+'sausage'='NOT A SAUSAGE'
'like' is the link.
Can you help me to learn more?
(Other definitions for not a sausage that I've seen before include "Zilch (colloquial)" , "zip" , "Absolutely nothing" , "Alternative to banger, maybe" , "diddly-squat" .)