Old and decrepit, fail to answer film star with animation (6,4)
I believe the answer is:
donald duck
'answer film star with animation' is the definition.
I can't judge whether this definition defines the answer.
'old and decrepit fail' is the wordplay.
'decrepit' is an anagram indicator.
'fail' becomes 'duck' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'old'+'and'='oldand'
'oldand' is an anagram of 'donald'.
'donald'+'duck'='DONALD DUCK'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for donald duck that I've seen before include "would be a figure of fun" , "Bradman getting no runs" , "bird apparently brought to life" , "Walt Disney character" , "Screen favourite" .)