Come down in pursuit of bachelor flat (5)
I believe the answer is:
bland
'flat' is the definition.
(I know that flat can be written as bland)
'come down in pursuit of bachelor' is the wordplay.
'come down' becomes 'land' (to land is to come down after flying).
'in pursuit of' means one lot of letters go next to another (some letters chase after others).
'bachelor' becomes 'B' (abbreviation e.g. BA=Bachelor of Arts).
'land' put after 'b' is 'BLAND'.
(Other definitions for bland that I've seen before include "Insipid, vapid" , "Insipid; lacklustre" , "Boring" , "without distinctive characteristics" , "Dull - tasteless" .)