Sweetener — because some in the morning needing energy (9)

I believe the answer is:

aspartame

'sweetener' is the definition.
(aspartame is a kind of sweetener)

'because some in the morning needing energy' is the wordplay.
'because' becomes 'as' (I've seen this in other clues).
'some' becomes 'part' (**).
'in the morning' becomes 'am'.
'needing' means one lot of letters go next to another.
'energy' becomes 'e' (physics symbol as in E=mca).
'as'+'part'+'am'+'e'='ASPARTAME'

(Other definitions for aspartame that I've seen before include "Strong artificial sweetener -- same apart (anag)" , "What sweetens" , "Sugar substitute" .)

I've seen this clue in The Times.

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