Sharp-eyed old maid, say, entertaining bishop (9)
I believe the answer is:
observant
'sharp-eyed' is the definition.
(I've seen this before)
'old maid say entertaining bishop' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'maid say' becomes 'servant' (maid is a kind of servant**).
'entertaining' indicates putting letters inside.
'bishop' becomes 'b' (abbreviation used in chess).
'o'+'servant'='oservant'
'oservant' going around 'b' is 'OBSERVANT'.
(Other definitions for observant that I've seen before include "Perceptive" , "taking things in" , "Keen-eyed" , "(Of music)using conventional keys" , "paying close attention" .)