Coach gutted to stop swimming lesson in lake (4,4)
I believe the answer is:
loch ness
'lake' is the definition.
(I know that Loch Ness is a loch)
'coach gutted to stop swimming lesson' is the wordplay.
'gutted' suggests removing the centre (to gut something is to remove its insides).
'to stop' means one lot of letters goes inside another (stopping can mean blocking a gap).
'swimming' indicates an anagram.
'coach' with its centre taken out is 'ch'.
'lesson' is an anagram of 'loness'.
'ch' inserted into 'loness' is 'LOCH NESS'.
'in' is the link.
(Other definitions for loch ness that I've seen before include "Scottish lake famed for mythical monster" , "Legendary Scottish apparition" , "Body of water in Scotland with legendary monster" , "Scottish water stretch with alleged monster" , "Scottish lake with mysterious monster" .)