Bard uses Old English in reduced part (4)
I believe the answer is:
poet
'bard uses' is the definition.
'poet' can be an answer for 'bard' (thesaurus). I'm not sure about the 'uses' bit.
'old english in reduced part' is the wordplay.
'old english' becomes 'oe'.
'in' means one lot of letters goes inside another.
'reduced part' becomes 'pt' (I've seen this in other clues. I am not sure about the 'reduced' bit.**).
'oe' placed into 'pt' is 'POET'.
(Other definitions for poet that I've seen before include "author" , "Bard" , "Heaney or Yeats, say" , "Tope with a versifier" , "Burns was one" .)