100 lines for eccentrics (6)
I believe the answer is:
cranks
'for eccentrics' is the definition.
(crank is a kind of eccentric)
'100 lines' is the wordplay.
'100' becomes 'C' (Roman numeral).
'lines' becomes 'ranks' (rank is a kind of line).
'c'+'ranks'='CRANKS'
(Other definitions for cranks that I've seen before include "Drugs" , "people irascible in America" , "People with crazy ideas" .)