Solidarity sends a mad car to lake (11)
I believe the answer is:
camaraderie
'solidarity' is the definition.
(thesaurus)
'sends a mad car to lake' is the wordplay.
'sends' is an anagram indicator (send can mean excite or stir).
'to lake' becomes 'erie' (Lake Erie is one of the Canadian/US 'Great Lakes').
'a'+'mad'+'car'='amadcar'
'amadcar' with letters rearranged gives 'camarad'.
'camarad'+'erie'='CAMARADERIE'
(Other definitions for camaraderie that I've seen before include "Friendly sociability" , "Mutual trust and friendship" , "Friendly feeling" , "all that backslapping?" , "Spirit of friendliness and trust" .)