Orville Wright keeps up satisfactorily (4)
I believe the answer is:
well
'satisfactorily' is the definition.
(synonyms)
'orville wright keeps up' is the wordplay.
'keeps' says the answer is hidden in the clue.
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'llew' is hidden within 'orville wright'.
'llew' written backwards gives 'WELL'.
(Other definitions for well that I've seen before include "Borehole" , "run" , "rise up" , "How one might like one's steak?" , "Very; deep shaft" .)