Earthy scent from lab dish shortened task (9)

'earthy scent' is the definition.
(smell of earth after rain)

'lab dish shortened task' is the wordplay.
'lab dish' becomes 'petri' (I've seen this in another clue).
'shortened' means to remove the last letter.
'task' becomes 'chore' (synonyms).
'chore' with its final letter taken away is 'chor'.
'petri'+'chor'='PETRICHOR'

'from' is the link.