Fall back, holding onto old American support for cause (8)
I believe the answer is:
espousal
'support for cause' is the definition.
(to espouse something is to publicly support it)
'fall back holding onto old american' is the wordplay.
I cannot quite understand how this works, but
'old' could be 'o' (common abbreviation eg in OE for Old English) and 'o' is located in the answer.
'american' could be 'usa' and 'usa' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for espousal that I've seen before include "Adoption (of a cause) - USA's pole (anag)" , "old-fashioned marriage" , "Action of adopting (a cause)" , "Backing, support" , "championship" .)