Poke right inside seedcase (4)
I believe the answer is:
Here is my best explanation:
'poke' is the definition.
('prod' can be a synonym of 'poke')
'right inside seedcase' is the subsidiary indication.
'right' becomes 'r' (common abbreviation).
'inside' indicates putting letters inside.
'seedcase' becomes 'pod' ('pod' can be a synonym of 'seedcase').
'r' going inside 'pod' is 'prod'.
(Other definitions for prod that I've seen before include "Poke, stimulate into action", "Poke - remind", "Poke, jab, nudge", "Poke with stiff finger to urge", "Jab, poke", "Provide stimulation", "Goad, stimulate into action", "Poke with a stick", "Stimulus" and "Motivate; jab".)