Give power to baleen swimming (6)
I believe the answer is:
enable
'give power to' is the definition.
(I've seen this in another clue)
'baleen swimming' is the wordplay.
'swimming' indicates an anagram (letters swim around into a new order).
'baleen' is an anagram of 'ENABLE'.
(Other definitions for enable that I've seen before include "Make possible, give the means to do something" , "Render capable" , "Activate" , "Facilitate or make possible" , "Make possible using baleen" .)