The tree for Irishmen? (3)
I believe the answer is:
fir
'the tree for irishmen?' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for fir that I've seen before include "Coniferous tree" , "Kind of cone-bearing tree" , "Evergreen conifer" , "Tree for Irishmen" , "Conifer tree" .)