Second generous specimen (6)
I believe the answer is:
sample
'specimen' is the definition.
(thesaurus)
'second generous' is the wordplay.
'second' becomes 's' (common abbreviation).
'generous' becomes 'ample' ('ample' can be similar in meaning to 'generous').
's'+'ample'='SAMPLE'
(Other definitions for sample that I've seen before include "Small part intended to represent the whole" , "instance" , "Small representative piece" , "Specimen, try out" , "Drop of" .)