Good lady relatively haggard (5)
I believe the answer is:
gaunt
'haggard' is the definition.
(synonyms)
'good lady relatively' is the wordplay.
'good' becomes 'g' (abbreviation).
'lady relatively' becomes 'aunt' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'g'+'aunt'='GAUNT'
Can you help me to learn more?
(Other definitions for gaunt that I've seen before include "Very thin especially from disease or hunger" , "Drawn" , "Lean and haggard" , "Bleak" , "birthplace of Edward's son" .)