Energy-packed tea with cooked item — it's not expensive (7)
I believe the answer is:
cheapie
'it's not expensive' is the definition.
(something cheap or inexpensive)
'energy-packed tea with cooked item' is the wordplay.
'energy' becomes 'e' (physics symbol as in E=mc2).
'packed' indicates putting letters inside (some letters are packed into others).
'tea' becomes 'cha' (cha is a type of tea).
'with' means one lot of letters go next to another.
'cooked item' becomes 'pie'.
'e' going inside 'cha' is 'chea'.
'chea'+'pie'='CHEAPIE'
(Other definitions for cheapie that I've seen before include "something economical" , "item knocked down?" , "Something inexpensive" .)