One takes in Canadian singer's claim to be short of energy (7)
I believe the answer is:
imbiber
'one takes in' is the definition.
(to imbibe is to consume or take in)
'canadian singer's claim to be short of energy' is the wordplay.
I cannot really understand how this works, but
'be' is found in the answer.
This explanation may well be incorrect...
(Other definitions for imbiber that I've seen before include "Sponge < and soak" , "Person who drinks" , "chap at the bar" , "one who keeps tumbler in hand" , ""I like a drink"" .)