Slow voyages round the pole (6)
I believe the answer is:
snails
'slow voyages round the pole' is the definition.
I can't tell whether this definition defines the answer.
'voyages round the pole' is the wordplay.
'voyages' becomes 'sails' ('sail' can be a synonym of 'voyage').
'round' indicates putting letters inside.
'the pole' becomes 'N' (abbreviation for North, as in North Pole).
'sails' enclosing 'n' is 'SNAILS'.
Can you help me to learn more?
(Other definitions for snails that I've seen before include "Air-breathing molluscs" , "oath" , "Soft-bodied animals with spiral shells, common in garden" , "Garden creatures" , "Gastropod molluscs" .)