President to equip puritan (4)
I believe the answer is:
prig
'puritan' is the definition.
(both can mean a prudish person)
'president to equip' is the wordplay.
'president' becomes 'p' (common abbreviation eg in VP).
'to equip' becomes 'rig' (rigging is a kind of equiping).
'p'+'rig'='PRIG'
(Other definitions for prig that I've seen before include "Snob" , "Smugly self-righteous person" , "Straight-laced person" , "Old maid" , "Smug hypocrite" .)