Reference some Gaelic item (4)
I believe the answer is:
cite
'reference' is the definition.
(to cite is to mention or quote)
'some gaelic item' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'CITE' is hidden within 'gaelic item'.
(Other definitions for cite that I've seen before include "Quote (a reference)" , "Quote (an author)" , "Quote as an example or in support" , "for instance" , "Summon - quote" .)