Speak well of a chap going round the bend
I believe the answer is:
'speak well of' is the definition.
(I've seen this in another clue)
'a chap going round the bend' is the wordplay.
'a chap' becomes 'lad' ('lad' can be a synonym of 'chap').
'going round' means one lot of letters goes inside another (some letters go around others).
'the bend' becomes 'U' (a U-bend is a kind of bend - pipe under sink).
'lad' enclosing 'u' is 'LAUD'.
(Other definitions for laud that I've seen before include "Praise acclaim" , "Archbishop of Canterbury, executed 1645" , "Give praise to" , "Praise formally" , "homage" .)