Take seat from empty, unclean Sierra and go off (8)
I believe the answer is:
unsaddle
'take seat' is the definition.
'unsaddle' can be an answer for 'take' (unsaddling is a kind of taking). I am not certain of the 'seat' bit.
'empty unclean sierra and go off' is the wordplay.
'empty' suggests removing the centre.
'sierra' becomes 's' (phonetic alphabet: alpha, bravo, charlie etc.).
'and' is a charade indicator (letters next to each other).
'go off' becomes 'addle' (eg an egg might addle).
'unclean' with its middle taken out is 'un'.
'un'+'s'+'addle'='UNSADDLE'
'from' is the link.
Can you help me to learn more?
(Other definitions for unsaddle that I've seen before include "Throw" , "Remove gear from horse" , "What to do after ride" , "tend horse" , "Remove the seat from a horse" .)