Slow voyage round the pole (5)
I believe the answer is:
snail
'slow' is the definition.
Although both the answer and definition are verbs in their base form, I can't understand how one could define the other.
'voyage round the pole' is the wordplay.
'voyage' becomes 'sail' (sail is a kind of voyage).
'round' means one lot of letters goes inside another.
'the pole' becomes 'N' (abbreviation for North, as in North Pole).
'sail' enclosing 'n' is 'SNAIL'.
Can you help me to learn more?
(Other definitions for snail that I've seen before include "Gastropod mollusc" , "dawdler" , "Slow-moving creature" , "Escargot" , "Proverbially slow-moving mollusc" .)