In secret, observe landlord (9)
I believe the answer is:
innkeeper
'landlord' is the definition.
(I've seen this before)
'in secret observe' is the wordplay.
'in' indicates putting letters inside.
'secret' becomes 'inner' (I've seen this in another clue).
'observe' becomes 'keep' (synonyms).
'inner' placed around 'keep' is 'INNKEEPER'.
(Other definitions for innkeeper that I've seen before include "local manager" , "Pub runner" , "Job" , "Mine host" , "Publican" .)