Paper run needing energy in the morning (4)
I believe the answer is:
ream
'paper' is the definition.
(I've seen this before)
'run needing energy in the morning' is the wordplay.
'run' becomes 'r' (cricket abbreviation).
'needing' means one lot of letters go next to another.
'energy' becomes 'e' (physics symbol as in E=mc2).
'in the morning' becomes 'am'.
'r'+'e'+'am'='REAM'
(Other definitions for ream that I've seen before include "Many sheets - enlarge hole" , "480 sheets of paper" , "20 quires of paper" , "516 sheets of paper" , "Quantity of paper, about 500 sheets" .)