Disease makes son shapely (6)
I believe the answer is:
scurvy
'disease' is the definition.
(scurvy is a kind of disease)
'son shapely' is the wordplay.
I cannot really see how this works, but
'son' could be 's' (genealogical abbreviation for son) and 's' is located in the answer.
The remaining letters 'curvy' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
'makes' is the link.
Can you help me to learn more?
(Other definitions for scurvy that I've seen before include "Whoreson" , "Sailors' old disease" , "Result of vitamin C deficiency" , "Disease - epithet for knave" , "Lime-juice prevented it" .)