This loch needs to be smooth for a learner (5)

'this loch' is the definition.
(I've seen this before)

'to be smooth for a learner' is the wordplay.
'to be smooth' becomes 'even' ('even' is associated in meaning with 'smooth').
'for' says to put letters next to each other (I've seen this in other clues).
'a learner' becomes 'l' (as in a learner driver with L-plates on their car).
'even' after 'l' is 'LEVEN'.

'needs' is the link.