Extremely tough words in puzzle (5)
I believe the answer is:
throw
'puzzle' is the definition.
(I know that puzzle is a more specific form of the action the throw)
'extremely tough words' is the wordplay.
'extremely' means to remove the middle letters (only the extremes of the word are used).
'words' becomes 'row' (synonyms).
'tough' with its middle taken out is 'th'.
'th'+'row'='THROW'
'in' is the link.
(Other definitions for throw that I've seen before include "Cast, lob" , "return from the boundary, perhaps" , "Cast, fling" , "Hurl; perplex" , "Deliberately lose" .)