Poor yours truly, crafty concealing answer! (6)
I believe the answer is:
measly
'poor' is the definition.
(I've seen this before)
'yours truly crafty concealing answer' is the wordplay.
'yours truly' becomes 'me' (the person that set this crossword).
'crafty' becomes 'sly' (sly can mean crafty or cunning).
'concealing' indicates putting letters inside.
'answer' becomes 'a' (abbreviation eg in Q and A).
'me'+'sly'='mesly'
'mesly' placed around 'a' is 'MEASLY'.
(Other definitions for measly that I've seen before include "'Contemptibly small, paltry (6)'" , "Poor" , "Mean, ungenerous" , "description of child's complaint" , "quite inadequate" .)