How to get had up for taking a back seat (6)
I believe the answer is:
howdah
'seat' is the definition.
(I know that howdah is a type of seat)
'how to get had up' is the wordplay.
'to get' means one lot of letters go next to another.
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'had' in reverse letter order is 'dah'.
'how'+'dah'='HOWDAH'
'for taking a back' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for howdah that I've seen before include "Who had a change on the elephant's back" , "Canopied elephant seat" , "seating?" , "Does it get you high for a trip" , "Seat fixed on an elephant" .)