Green’s Dictionary of Slang

(Irish) cunning, clever.

1986		P. O’Farrell Tell me, Sean O’Farrell 81: Taking advantage of the great number of Thomond-men lost in the battle the glick (wily) Desmonds demanded that one of theirs should assume the throne.
1996		(ref. to 1963) D. Healy Bend for Home 162: We all know about you, you glick fucker.