Gravity unit right for one beyond hope (5)
I believe the answer is:
goner
'one beyond hope' is the definition.
(I've seen this before)
'gravity unit right' is the wordplay.
'gravity' becomes 'g'.
'unit' becomes 'one' (synonyms).
'right' becomes 'r' (common abbreviation).
'g'+'one'+'r'='GONER'
'for' is the link.
(Other definitions for goner that I've seen before include "Someone beyond help" , "one with no future" , "One doomed to die" , "I'm late" , "person about to depart" .)