A girl always seen in wellies (5)
I believe the answer is:
'a girl' is the definition.
'in wellies' is the wordplay.
'in' indicates the answer is hidden within the clue.
'ELLIE' is hidden in the letters of 'wellies'.
'always seen' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for ellie that I've seen before include "a wake-up call" , "Diminutive girl" , "Little Eleanor" , "Name of girl in The Water Babies (Kingsley)" , "woman" .)