Suit man working for a big rise in the main? (7)
I believe the answer is:
tsunami
'a big rise in the main?' is the definition.
(the main can mean the sea)
'suit man working' is the wordplay.
'working' indicates anagramming the letters.
'suit'+'man'='suitman'
'suitman' anagrammed gives 'TSUNAMI'.
'for' is the link.
(Other definitions for tsunami that I've seen before include "crashing bore" , ""Harbour wave"" , "Large tidal wave" , "Destructive tidal wave" , "Seismic sea wave" .)