Study agreement in speech (3)
I believe the answer is:
eye
'study' is the definition.
(both can mean to examine)
'agreement in speech' is the wordplay.
'agreement' becomes 'ay'.
'in speech' shows a homophone (sound like).
'ay' sounds like 'EYE'.
(Other definitions for eye that I've seen before include "Observe narrowly" , "Organ of sight" , "where the pupil is seated" , "Ireland's . . ., off the Dublin coast" , "20 [OBSERVE]" .)