Romeo had abandoned the provision to be upright (8)
I believe the answer is:
headroom
'provision to be upright' is the definition.
I can't tell whether this defines the answer.
'romeo had abandoned' is the wordplay.
'abandoned' indicates an anagram (the original order is abandoned).
'romeo'+'had'='romeohad'
'romeohad' with letters rearranged gives 'HEADROOM'.
'the' acts as a link.
Can you help me to learn more?
(Other definitions for headroom that I've seen before include "vertical space" , "Clearance below a bridge or ceiling" , "enough space" , "Space available above" , "Clearance vertically" .)