Sheep from Ireland seen in a moment (6)
I believe the answer is:
merino
'sheep' is the definition.
(breed of sheep)
'ireland seen in a moment' is the wordplay.
'ireland' becomes 'Erin' (poetic name for Ireland).
'seen in' means one lot of letters goes inside another.
'a moment' becomes 'mo' (as in 'just a mo').
'erin' going inside 'mo' is 'MERINO'.
'from' acts as a link.
(Other definitions for merino that I've seen before include "Fine woollen yarn" , "Sheep with fine quality fleece" , "Fine soft woolen yarn" , "Type of sheep" , "Sheep from Spain with a heavy quality fleece" .)