Grand relative, haggard (5)
I believe the answer is:
gaunt
'haggard' is the definition.
(I know that haggard can be written as gaunt)
'grand relative' is the wordplay.
'grand' becomes 'G' (G is short for ground as in a thousand).
'relative' becomes 'aunt' (aunt is a kind of relative).
'g'+'aunt'='GAUNT'
(Other definitions for gaunt that I've seen before include "Thin and pinched" , "place associated with Edward III's son" , "Lean and haggard" , "Very thin, cadaverous" , "Very slight" .)