Produce DNA sequence with speed (8)
I believe the answer is:
generate
'produce' is the definition.
(generating is a kind of producing)
'dna sequence with speed' is the wordplay.
'dna sequence' becomes 'gene' (I've seen this before).
'with' says to put letters next to each other.
'speed' becomes 'rate' (rate is a kind of speed).
'gene'+'rate'='GENERATE'
(Other definitions for generate that I've seen before include "Produce, electricity say" , "Give rise to" , "Engender" , "Make" , "24 across (anag)" .)