Compare Liz with Boris's predecessor - we mustn't have her back (5)
I believe the answer is:
liken
'compare' is the definition.
(I know that compare can be written as liken)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for liken that I've seen before include "Represent as similar" , "Equate" , "Compare" , "Point out the resemblance (to)" .)