Chap, having energy, can wave (8)
I believe the answer is:
greeting
'wave' is the definition.
(thesaurus)
'chap having energy can' is the wordplay.
'chap' becomes 'greg' ().
'having' is an insertion indicator.
'energy' becomes 'e' (physics symbol as in E=mcr).
'can' becomes 'tin' (both are metal containers).
'e'+'tin'='etin'
'greg' going around 'etin' is 'GREETING'.
(Other definitions for greeting that I've seen before include "Word of welcome" , "Welcoming" , "Word(s) of welcome" , "Hello" , "causes weeping for some" .)