End first appeared like a mule (8)
I believe the answer is:
stubborn
'like a mule' is the definition.
(I've seen this in another clue)
'end first appeared' is the wordplay.
'end' becomes 'stub' (eg the stub of a cigarette).
'first appeared' becomes 'born' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'stub'+'born'='STUBBORN'
Can you help me to learn more?
(Other definitions for stubborn that I've seen before include "Unwilling to yield or grant a point" , "Obstinate, unyielding" , "Unreasonably unwilling to change" , "Wilful" , "Sticky" .)