Plant in swamp around the end of winter (4)
I believe the answer is:
fern
'plant' is the definition.
(fern is a kind of plant)
'swamp around the end of winter' is the wordplay.
'swamp' becomes 'fen' (I've seen this in another clue).
'around' is an insertion indicator.
'the end of' suggests the final letters.
The final letter of 'winter' is 'r'.
'fen' going around 'r' is 'FERN'.
'in' acts as a link.
(Other definitions for fern that I've seen before include "Plant such as bracken" , "Non-flowering plant" , "A frond is its leaf" , "Plant producing spores" , "Feathery-leaved plant" .)