Many go mad with desire (5)
I believe the answer is:
crave
'desire' is the definition.
(craving is a kind of desiring)
'many go mad' is the wordplay.
'many' becomes 'c' (C is the Roman numeral for 100).
'go mad' becomes 'rave'.
'c'+'rave'='CRAVE'
'with' is the link.
(Other definitions for crave that I've seen before include "Yearn for (something)" , "Desperately desire" , "Have strong urge" , "Hunger for" , "Feel a powerful desire for (something)" .)