Tense over the border? (2,4)
I believe the answer is:
on edge
'tense' is the definition.
(thesaurus)
'over the border?' is the wordplay.
'over' becomes 'on' (I've seen this in other clues).
'the border?' becomes 'edge' (border is a kind of edge**).
'on'+'edge'='ON EDGE'
(Other definitions for on edge that I've seen before include "'Tense, nervous (2,4)'" , "close to border" , "Apprehensive" , "Nervously excited" , "All agog" .)