Ears reshaped by source of light — surgical beam? (5)
I believe the answer is:
laser
'surgical beam?' is the definition.
(as in laser surgery)
'ears reshaped by source of light' is the wordplay.
'reshaped' is an anagram indicator.
'by' means one lot of letters go next to another.
'source of' suggests taking the first letters (the start - or source - of the word).
The first letter of 'light' is 'l'.
'ears' anagrammed gives 'aser'.
'aser' put after 'l' is 'LASER'.
(Other definitions for laser that I've seen before include "Surgical device" , "Beam (used in surgery)" , "Coherent light source" , "Generator of beam" , "scientific device" .)