Attentive old British employee (9)
I believe the answer is:
observant
'attentive' is the definition.
(similar in meaning)
'old british employee' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'employee' becomes 'servant' (I've seen this before).
'o'+'b'+'servant'='OBSERVANT'
(Other definitions for observant that I've seen before include "Good at noticing" , "Likely to notice" , "Perceptive" , "with a keen eye" , "(Of music)using conventional keys" .)