Took account of empty theatre in sign of agreement (5)
I believe the answer is:
noted
'took account of' is the definition.
(I've seen this before)
'empty theatre in sign of agreement' is the wordplay.
'empty' means to remove the middle letters.
'in' indicates putting letters inside.
'sign of agreement' becomes 'nod' (I've seen this before).
'theatre' with its middle removed is 'te'.
'te' inserted within 'nod' is 'NOTED'.
(Other definitions for noted that I've seen before include "written down" , "Toned down and recorded" , "Observed - famous" , "Toned (anag.)" , "Famous or eminent" .)