It's dead good touching sweetheart! (4)
I believe the answer is:
gone
'it's dead' is the definition.
(similar in meaning)
'good touching sweetheart' is the wordplay.
'good' becomes 'g' (abbreviation).
'touching' becomes 'on' ().
'sweetheart' becomes 'e' (the middle letter or heart of 'sweet').
'g'+'on'+'e'='GONE'
(Other definitions for gone that I've seen before include "Departed or dead" , "Away, departed" , "Departed, left" , "Departed or no longer available" , "Moved - died" .)