Tendency of Democrat to crack (5)
I believe the answer is:
drift
'tendency' is the definition.
(I know that drift is a type of tendency)
'democrat to crack' is the wordplay.
'democrat' becomes 'd'.
'to crack' becomes 'rift' (rift is a kind of crack).
'd'+'rift'='DRIFT'
'of' is the link.
(Other definitions for drift that I've seen before include "move around without end" , "Move with the current" , "spirit" , "(Of snow) blow into heaps" , "Gist - snow" .)