Produce straight lines say (5)
I believe the answer is:
raise
'produce' is the definition.
(I know that produce can be written as raise)
'straight lines say' is the wordplay.
'straight lines' becomes 'rays' (I've seen this before).
'say' shows a homophone (sound like).
'rays' sounds like 'RAISE'.
(Other definitions for raise that I've seen before include "Make greater" , "Lift up, bring up" , "Bring up - an increase in pay" , "Cultivate by growing" , "Produce" .)