Did some gardening, brick-carrier saving energy (4)
I believe the answer is:
hoed
'did some gardening' is the definition.
(to hoe is to garden with a hoe)
'brick-carrier saving energy' is the wordplay.
'brick carrier' becomes 'hod' (I've seen this before).
'saving' is an insertion indicator.
'energy' becomes 'e' (physics symbol as in E=mc2).
'hod' placed around 'e' is 'HOED'.
(Other definitions for hoed that I've seen before include "Tended to soil" , "Weeded" .)