Analyse sample from feldspar seam (5)
I believe the answer is:
parse
'analyse' is the definition.
(to parse is to analyse grammatically)
'sample from feldspar seam' is the wordplay.
'sample from' indicates a hidden word (a sample of letters from the clue).
'PARSE' can be found hidden inside 'feldspar seam'.
(Other definitions for parse that I've seen before include "Deconstruct grammatically" , "do grammatical analysis" , "analyse this, for instance" , "Analyse sentence" , "Analyse grammatically" .)