Swimmer sculls up and down fluidly, ignoring slight hiccup at first (9)
I believe the answer is:
swordfish
'swimmer' is the definition.
(I've seen this before)
'down fluidly ignoring slight hiccup at first' is the wordplay.
'down' becomes 'sword' (I can't explain this - if you can you should give a lot more credence to this answer).
'at first' indicates taking the first letters.
The initial letters of 'fluidly ignoring slight hiccup' is 'fish'.
'sword'+'fish'='SWORDFISH'
'sculls up and' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for swordfish that I've seen before include "seafood" , "sea food" , "(Edible) long-snouted swimmer" , "Xiphius gladius" , "Marine creature with very long upper jaw" .)