Rather unpleasant fellow, say, always turning up (2,1,6)
I believe the answer is:
to a degree
'rather' is the definition.
(I've seen this before)
'unpleasant fellow say always turning up' is the wordplay.
'unpleasant fellow' becomes 'toad' (term for a contemptible person).
'say' becomes 'eg'.
'always' becomes 'eer' (poetic way of saying ever).
'turning up' says the letters should be written in reverse.
'eer' in reverse letter order is 'ree'.
'toad'+'eg'+'ree'='TO A DEGREE'
(Other definitions for to a degree that I've seen before include "How undergraduate works" , "Where some university courses lead" , "though not entirely" , "Somewhat" , "Where students are heading" .)