Move smoothly as rowing teams in sound (6)
I believe the answer is:
cruise
'move smoothly' is the definition.
'rowing teams in sound' is the wordplay.
'rowing teams' becomes 'crews'.
'in sound' indicates a 'sounds like' (homophone) clue.
'crews' sounds like 'CRUISE'.
'as' acts as a link.
(Other definitions for cruise that I've seen before include "Holiday at sea" , "Sail around" , "Sea trip" , "journey" , "Coast" .)