Singer has energy to shout encouragement (5)
I believe the answer is:
cheer
'shout encouragement' is the definition.
(I've seen this before)
'singer has energy' is the wordplay.
'singer' becomes 'cher' (American singer).
'has' means one lot of letters goes inside another.
'energy' becomes 'e' (physics symbol as in E=mc2).
'cher' placed around 'e' is 'CHEER'.
'to' is the link.
(Other definitions for cheer that I've seen before include "Shout of praise or joy" , "Encouraging shout" , "Shout hooray" , "Give comfort or support to" , "Applaud; mood" .)