Yours truly is to continue without single idea (10)
I believe the answer is:
impression
'idea' is the definition.
(impression is a kind of idea)
'yours truly is to continue without single' is the wordplay.
'yours truly is' becomes 'I'm'.
'to continue' becomes 'presson' (to press on with something is to continue with it).
'without' means one lot of letters goes inside another ('without' can be similar in meaning to 'outside').
'single' becomes 'I' (one).
'presson' going around 'i' is 'pression'.
'im'+'pression'='IMPRESSION'
(Other definitions for impression that I've seen before include "Feeling; print" , "Imitation (of a person)" , "take-off" , "Mark" , "opinion" .)