__ year (2024 or 2028) (4)
'year' is the definition.
(synonyms)
This is all the clue.
(Another definition for twelvemonth that I've seen is " year".)
(Other definitions for leap that I've seen before include "Sudden surge" , "Jump; type of year" , "identify extra day?" , "some years?" , "Pounce" .)
(Other definitions for gap that I've seen before include "Small opening" , "Break in continuity" , "Empty space between things" , "A small parting, in hedge or teeth" , "Break, hole, space" .)