Suggest upgrade to rear lift (5)
I believe the answer is:
raise
I believe this clue is a quadruple definition!!
'suggest' is the first definition.
(I've seen this in another clue)
'upgrade' is the second definition.
(both can mean to promote or improve)
'to rear' is the third definition.
(synonyms)
'lift' is the fourth definition.
(I know that lift can be written as raise)
(Other definitions for raise that I've seen before include "Make greater" , "climb" , "cairn" , "Heighten" , "Uplift" .)