Lanky Scots go on heather (8)
I believe the answer is:
gangling
'lanky' is the definition.
('gangling' can be a synonym of 'lanky')
'scots go on heather' is the wordplay.
'scots go' becomes 'gang' (go in scots is gang).
'on' means one lot of letters go next to another.
'heather' becomes 'ling' ('ling' can be a synonym of 'heather').
'gang'+'ling'='GANGLING'
(Other definitions for gangling that I've seen before include "moving awkwardly" , "Lanky" , "Rawboned" , "Tall and thin" .)