Unemotional fish going round lake (4)
I believe the answer is:
cold
'unemotional' is the definition.
(I've seen this in another clue)
'fish going round lake' is the wordplay.
'fish' becomes 'cod' (type of fish).
'going round' indicates putting letters inside (some letters go around others).
'lake' becomes 'L' (geographical abbreviation).
'cod' placed around 'l' is 'COLD'.
(Other definitions for cold that I've seen before include "Chilly; unemotional" , "Lacking emotion" , "Stand-offish" , "Dead" , "Unfriendly" .)