Softballer generally limits pollen (8)
I believe the answer is:
allergen
'pollen' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'softballer generally limits' is the wordplay.
'limits' says the answer is hidden in the clue (the answer is surrounded or limited by the clue).
'ALLERGEN' can be found hidden inside 'softballer generally'.
Can you help me to learn more?
(Other definitions for allergen that I've seen before include "Protein" , "Any substance that causes a hypersensitive reaction" , "Substance causing bodily reaction" , "Irritant" , "Disagreeable food component" .)