Spring beside Scottish lake showing good health (8)
I believe the answer is:
wellness
'good health' is the definition.
(I've seen this in another clue)
'spring beside scottish lake' is the wordplay.
'spring' becomes 'well' (both can mean a source of water).
'beside' means one lot of letters go next to another (I've seen this in other clues).
'scottish lake' becomes 'ness' (I've seen this in another clue).
'well'+'ness'='WELLNESS'
'showing' acts as a link.
(Other definitions for wellness that I've seen before include "Health" , "good condition" .)