Showed agreement when drowsy? (6)
I believe the answer is:
nodded
'showed' is the definition.
The definition and answer can be both to do with communicating as well as being past participle verbs.
Maybe you can see an association between them that I don't see?
'agreement when drowsy?' is the wordplay.
'agreement' becomes 'nod' (a nod indicates agreement).
'when drowsy?' becomes 'ded' (I can't justify this - if you can you should believe this answer much more).
'nod'+'ded'='NODDED'
Can you help me to learn more?
(Other definitions for nodded that I've seen before include "Indicated assent or recognition" , "Signalled agreement" , "signed agreement" , "Bent the head in sleepiness" , "Signalled yes" .)