Poor medium I left without difficulty (6)
I believe the answer is:
measly
'poor' is the definition.
(I've seen this before)
'medium i left without difficulty' is the wordplay.
'medium' becomes 'm' (as in UK clothing sizes).
'left' indicates named letters should be taken away.
'without difficulty' becomes 'easily' (synonyms).
'easily' with 'i' taken out is 'easly'.
'm'+'easly'='MEASLY'
(Other definitions for measly that I've seen before include "'Contemptibly small, paltry (6)'" , "ungenerous in amount" , "Poor" , "Insignificant a having spots!" , "Spotty - paltry" .)