Say hello to Lofty (4)
I believe the answer is:
high
'lofty' is the definition.
(similar in meaning)
'say hello' is the wordplay.
'say' indicates a 'sounds like' (homophone) clue.
'hello' becomes 'hi' (synonyms).
'hi' sounds like 'HIGH'.
'to' acts as a link.
(Other definitions for high that I've seen before include "(Of meat) slightly decomposed" , "on a trip" , "At altitude" , "Going off - in great spirits" , "Important; drugged" .)