Conscious of a town in Herts (5)
I believe the answer is:
aware
'conscious of' is the definition.
(being conscious means being aware of something)
'a town in herts' is the wordplay.
'town in herts' becomes 'ware' (I can't explain this - if you can you should give a lot more credence to this answer).
'a'+'ware'='AWARE'
Can you help me to learn more?
(Other definitions for aware that I've seen before include "Knowing (of something)" , "Acquainted with or conscious of" , "Acquainted with or mindful of" , "well informed" , "Alert, conscious of" .)