Look serious about good spring that produces life in pond (9)
I believe the answer is:
frogspawn
'that produces life in pond' is the definition.
(frog eggs)
'look serious about good spring' is the wordplay.
'look serious' becomes 'frown' (a frown is a serious expression).
'about' means one lot of letters goes inside another.
'good' becomes 'g' (abbreviation).
'spring' becomes 'spa' (spa can mean a mineral spring).
'g'+'spa'='gspa'
'frown' placed around 'gspa' is 'FROGSPAWN'.
(Other definitions for frogspawn that I've seen before include "eggs?" , "Future tadpoles" , "amphibian's offspring" .)