Remnant of a letter to artless Stuart (4)
I believe the answer is:
stub
'remnant' is the definition.
(thesaurus)
'a letter to artless stuart' is the wordplay.
'a letter' becomes 's'.
'to artless stuart' becomes 'tub' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
's'+'tub'='STUB'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for stub that I've seen before include "Counterfoil, of a cheque say" , "this pollution by smoker?" , "Put out" , "End of cigarette or counterfoil of cheque" , "seen in the ash-tray" .)