Can you not go quite so far as to sit on it? (4)
I believe the answer is:
sofa
'can you not go quite so far as' is the definition.
I can't tell whether this defines the answer.
'sit on it?' is the wordplay.
'sit' becomes 'of' (I can't explain this - if you can you should believe this answer much more).
'on' means one lot of letters goes inside another.
'it?' becomes 'sa' (old-fashioned abbreviation for sex appeal).
'of' placed within 'sa' is 'SOFA'.
'to' acts as a link.
Can you help me to learn more?
(Other definitions for sofa that I've seen before include "Upholstered seat for two or more" , "Divan" , "Chesterfield, maybe" , "Upholstered seating" , "Long upholstered seat with back and arms" .)