Swimmer blocked by fool getting raised pulse, perhaps (6)
I believe the answer is:
legume
'pulse perhaps' is the definition.
(pulse is a kind of legume)
'swimmer blocked by fool getting raised' is the wordplay.
'swimmer' becomes 'eel' (eel is a type of fish).
'blocked by' means one lot of letters goes inside another (I've seen this in other clues).
'fool' becomes 'mug' (synonyms).
'getting raised' says the letters should be written in reverse (in a down clue, letters go up).
'eel' going around 'mug' is 'emugel'.
'emugel' written backwards gives 'LEGUME'.
(Other definitions for legume that I've seen before include "Pea-family crop plant" , "Pea or bean pod" , "Bean or pea, for example" , "A vegetable for e.g. mule" , "A fruit that bears its seed in pods" .)