Changes as to fodder (4)
I believe the answer is:
oats
'fodder' is the definition.
(I've seen this in another clue)
'changes as to' is the wordplay.
'changes' is an anagram indicator.
'as'+'to'='asto'
'asto' is an anagram of 'OATS'.
(Other definitions for oats that I've seen before include "Food for horses and Scots (said Dr Johnson)" , "Grains or porridge" , "Wild ones are sown in youthful excess" , "Young folk might sow wild ones" , "Edible grass seeds" .)