Sounds like greeting in gym was a publicity stunt (4)
I believe the answer is:
hype
'publicity stunt' is the definition.
(I've seen this before)
'sounds like greeting in gym was a' is the wordplay.
I cannot quite understand how this works, but
'like' could be 'y' (similar in meaning) and 'y' is found in the answer.
'gym' could be 'pe' (short for Physical Education) and 'pe' is located in the answer.
A single letter 'h' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for hype that I've seen before include "Agitate" , "Doer of dirty work" , "Misleadingly exaggerated publicity" , "Exaggerated advocacy" , "injection" .)