A line crossed by nudist in Darwin? (10)
I believe the answer is:
naturalist
'darwin?' is the definition.
(darwin is a kind of naturalist)
'a line crossed by nudist' is the wordplay.
'line' becomes 'l' (used when specifying particular lines from a poem).
'crossed by' indicates putting letters inside (inserted letters are crossed or covered by others).
'nudist' becomes 'naturist' (synonyms).
'a'+'l'='al'
'al' inserted inside 'naturist' is 'NATURALIST'.
'in' is the link.
(Other definitions for naturalist that I've seen before include "Zoology expert possibly" , "Zoologist" , "one's studying in the wild" , "One who studies animals and plants" , "Student of zoology or botany" .)