Second home in country landing tax once (4)
I believe the answer is:
scot
'tax once' is the definition.
(historical term for a type of tax)
'second home in country' is the wordplay.
'second' becomes 's' (common abbreviation).
'home in country' becomes 'cot' (archaic term for a cottage).
's'+'cot'='SCOT'
'landing' acts as a link.
(Other definitions for scot that I've seen before include "Aberdonian perhaps" , "Native of northern Great Britain" , "Burns for one" , "Glaswegian, say" , "North Briton" .)