Contemptuous of runs arranged crossing cold lake (8)
I believe the answer is:
scornful
'contemptuous' is the definition.
('scornful' can be a synonym of 'contemptuous')
'of runs arranged crossing cold lake' is the wordplay.
'arranged' is an anagram indicator.
'crossing' indicates putting letters inside.
'cold' becomes 'c' (eg on taps).
'lake' becomes 'l'.
'of'+'runs'='ofruns'
'ofruns' anagrammed gives 'sornfu'.
'sornfu' enclosing 'c' is 'scornfu'.
'scornfu'+'l'='SCORNFUL'
(Other definitions for scornful that I've seen before include "Dismissive, contemptuous" , "Openly contemptuous" , "Expressing extreme contempt" , "Mocking" , "Contemptuous or derisive" .)