Nymph gives companion love by edge of lake (4)
I believe the answer is:
echo
'nymph' is the definition.
(figure of Greek myth)
'companion love by edge of lake' is the wordplay.
'companion' becomes 'ch' (Companion of Honour).
'love' becomes 'o' (love means zero in tennis).
'by' is a charade indicator (letters next to each other).
'edge of' suggests the final letters (one of the letters on the edge of the word).
The last letter of 'lake' is 'e'.
'ch'+'o'='cho'
'cho' put after 'e' is 'ECHO'.
'gives' acts as a link.
(Other definitions for echo that I've seen before include "One who slavishly copies" , "Close imitation" , "repercussion" , "What evokes memories" , "Reminder" .)