Sharp-eyed old maid, perhaps, smothers bachelor (9)
I believe the answer is:
observant
'sharp-eyed' is the definition.
(I've seen this before)
'old maid perhaps smothers bachelor' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'maid perhaps' becomes 'servant' (maid is a kind of servant**).
'smothers' means one lot of letters goes inside another (I've seen this in other clues).
'bachelor' becomes 'b' (abbreviation e.g. BA=Bachelor of Arts).
'o'+'servant'='oservant'
'oservant' going around 'b' is 'OBSERVANT'.
(Other definitions for observant that I've seen before include "Perceptive" , "(Of music)using conventional keys" , "Orthodox" , "Good at noticing" , "adhering to religious practices" .)