Weary, saving energy in rows (6)
I believe the answer is:
tiered
'in rows' is the definition.
(I've seen this before)
'weary saving energy' is the wordplay.
'weary' becomes 'tired' ('tired' can be similar in meaning to 'weary').
'saving' is an insertion indicator.
'energy' becomes 'e' (physics symbol as in E=mc2).
'tired' enclosing 'e' is 'TIERED'.
(Other definitions for tiered that I've seen before include "Arranged in rising 5 ac" , "in racks, say" , "In ranks" , "Laid out in layers, like wedding cake" , "Arranged in rows" .)