Support collapsing rule in East Germany (8)
I believe the answer is:
underlie
'support' is the definition.
(I've seen this before)
'collapsing rule in east germany' is the wordplay.
'collapsing' indicates anagramming the letters.
'east' becomes 'e' ('E' can be a synonym of 'east').
'germany' becomes 'd' (international vehicle registration code).
'rule'+'in'+'e'+'d'='ruleined'
'ruleined' with letters rearranged gives 'UNDERLIE'.
(Other definitions for underlie that I've seen before include "Form the base for" , "Be subject to" , "Prove to be base" , "Be situated below" , "Be the basis of" .)