Unusually achy time in sailing boat (5)
I believe the answer is:
yacht
'sailing boat' is the definition.
(I've seen this before)
'unusually achy time' is the wordplay.
'unusually' indicates anagramming the letters.
'time' becomes 't'.
'achy' anagrammed gives 'yach'.
'yach'+'t'='YACHT'
'in' acts as a link.
(Other definitions for yacht that I've seen before include "Sailing or motor vessel for cruising or racing" , "Sailboat" , "Light sailing-vessel for sport" , "Pleasure craft" , "Luxury purchase" .)