Finally securing a little energy: that's something (2,5)
I believe the answer is:
at least
'that's something' is the definition.
(oh well, that's something at least)
'finally securing a little energy' is the wordplay.
'finally' becomes 'at last' (synonyms).
'securing' means one lot of letters goes inside another.
'a little' suggests taking the first letters.
The first letter of 'energy' is 'e'.
'atlast' placed around 'e' is 'AT LEAST'.
(Other definitions for at least that I've seen before include "As a minimum" , "however" , "'If nothing else (2,5)'" , "Eat salt (anag) - if nothing else" , "Anyway" .)