Long jumper doesn't want strong field (3)
I believe the answer is:
lea
'field' is the definition.
(lea can mean a meadow or field of grass)
'long jumper doesn't want strong' is the wordplay.
I cannot really see how this works, but
'long' could be 'l' and 'l' is present in the answer.
The remaining letters 'ea' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for lea that I've seen before include "Open arable land (poet.)" , "Tract of pastureland" , "'The lowing herd wind slowly o'er the . . .'" , "Land growing grass" , "''The lowing herd winds slowly o'er the ... '' (Gray)" .)