Release bricks (about ton) (3,2)
I believe the answer is:
let go
'release' is the definition.
(synonyms)
'bricks about ton' is the wordplay.
'bricks' becomes 'lego' (plastic brick toys).
'about' means one lot of letters goes inside another.
'ton' becomes 't' (abbreviation).
'lego' going around 't' is 'LET GO'.
(Other definitions for let go that I've seen before include "Release - relax one's grasp" , "Don't hold on" , "Release or permit to depart" , "Set at liberty, loose grip on" , "Relinquish one's grip" .)