Worker entertaining Durham's first venerable historian (4)
I believe the answer is:
bede
'venerable historian' is the definition.
(I've seen this in another clue)
'worker entertaining durham's first' is the wordplay.
'worker' becomes 'bee' (a worker bee).
'entertaining' means one lot of letters goes inside another (inviting in, as for dinner).
'durham's first' becomes 'd' (bst letter of 'durham').
'bee' placed around 'd' is 'BEDE'.
(Other definitions for bede that I've seen before include "Ancient English historian" , "Historian saint; Eliot's Adam" , "Old historian" , "Adam ___, novel by George Eliot" , "'Venerable' English monk" .)