A canvas by Lowry originally undeveloped (6)
I believe the answer is:
latent
'undeveloped' is the definition.
(thesaurus)
'a canvas by lowry originally' is the wordplay.
'canvas' becomes 'tent' (I've seen this in other clues).
'by' says to put letters next to each other.
'originally' indicates taking the first letters.
The initial letter of 'lowry' is 'l'.
'a'+'tent'='atent'
'atent' after 'l' is 'LATENT'.
(Other definitions for latent that I've seen before include "Hidden (potential)" , "As yet undeveloped" , "'Hidden, undeveloped (6)'" , "Existing but not yet manifest" , "Potentially existing but not presently evident" .)