Scots one flourishing at last in ram tethering (5,2)

'tethering' is the definition.
(to tie something up is to tether it)

'scots one flourishing at last in ram' is the wordplay.
'scots one' becomes 'yin' (Scottish dialect term for 'one').
'at last' says to take the final letters.
'in' means one lot of letters goes inside another.
'ram' becomes 'tup' (both can mean a male sheep).
The last letter of 'flourishing' is 'g'.
'yin'+'g'='ying'
'ying' put into 'tup' is 'TYING UP'.