Awkward ascent by an unusually calm rebel retreating after making the Spanish quit (7)
I believe the answer is:
clamber
'rebel retreating after making the spanish quit' is the definition.
I can't judge whether this defines the answer.
'awkward ascent by an unusually calm' is the wordplay.
'awkward ascent' becomes 'ber' (I can't explain this - if you can you should give a lot more credence to this answer).
'by' means one lot of letters go next to another.
'an unusually' is an anagram indicator.
'calm' anagrammed gives 'clam'.
'ber' put after 'clam' is 'CLAMBER'.
Can you help me to learn more?
(Other definitions for clamber that I've seen before include "Climb using hands and feet" , "Scramble awkwardly" , "Scale awkwardly" , "Climb awkwardly (over something)" .)