Expert that’s backed politician after start of debacle is to flee (6)
I believe the answer is:
decamp
'to flee' is the definition.
(decamping is a kind of fleeing)
'expert that's backed politician after start of debacle' is the wordplay.
'expert' becomes 'ace' (ace is a kind of expert**).
'that's backed' says the letters should be written in reverse.
'politician' becomes 'mp'.
'after' says to put letters next to each other.
'start of' says to take the initial letters.
The first letter of 'debacle' is 'd'.
'ace' reversed gives 'eca'.
'eca'+'mp'='ecamp'
'ecamp' after 'd' is 'DECAMP'.
'is' is the link.
(Other definitions for decamp that I've seen before include "Mizzle" , "Go away suddenly or secretly - leaving tent?" , "Move on" , "Depart suddenly or secretly" , "Do a runner" .)