Echo around, or send back (7)
I believe the answer is:
endorse
'back' is the definition.
('endorse' can be a synonym of 'back')
'echo around or send' is the wordplay.
'echo' becomes 'e' (phonetic alphabet: alpha, bravo, charlie etc.).
'around' is an anagram indicator.
'or'+'send'='orsend'
'orsend' is an anagram of 'ndorse'.
'e'+'ndorse'='ENDORSE'
(Other definitions for endorse that I've seen before include "Sore end (anag.)" , "Say you approve" , "Corroborate" , "Pass" , "Ratify" .)