Agile Romeo embraced by Mata Hari? (4)
I believe the answer is:
spry
'agile' is the definition.
('spry' can be a synonym of 'agile')
'romeo embraced by mata hari?' is the wordplay.
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'embraced by' means one lot of letters goes inside another.
'mata hari?' becomes 'spy' (mata hari is a kind of spy).
'r' going within 'spy' is 'SPRY'.
(Other definitions for spry that I've seen before include "Sprightly" , "'Active and lively, nimble (4)'" , "Energetic" , "Lively (especially of an older person)" , "Light on one's feet" .)