Country singer Jackson (4)
I believe the answer is:
alan
'country singer jackson' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for alan that I've seen before include "Boy" , "A.A. Milne's first name" , "-- Turing, mathematician" , "- Bennett, English dramatist, author" , "-- Ayckbourn, English dramatist" .)