Bleak start for Doctor Foster (5)
I believe the answer is:
drear
'bleak' is the definition.
(thesaurus)
'start for doctor foster' is the wordplay.
'start for' suggests taking the first letters.
'foster' becomes 'rear' (I've seen this before).
The initial letter of 'doctor' is 'd'.
'd'+'rear'='DREAR'
(Other definitions for drear that I've seen before include "Grim" , "grave" , "gloomy in poem" , "Dismal (literary)" , "Gloomy and cheerless" .)