Spanish gentleman leading an ass (6)
I believe the answer is:
donkey
'an ass' is the definition.
(donkey is a kind of ass)
'spanish gentleman leading' is the wordplay.
'spanish gentleman' becomes 'don' (I've seen this in another clue).
'leading' becomes 'key' (I can't justify this - if you can you should believe this answer much more).
'don'+'key'='DONKEY'
Can you help me to learn more?
(Other definitions for donkey that I've seen before include "Dunce" , "Braying quadruped" , "Mary's transport" , "Garment associated with building workers" , "Fool" .)