Squeeze (5)
'squeeze' is the definition.
(synonyms)
This is all the clue.
(Other definitions for press that I've seen before include "Squeeze - newspapers - push" , "Iron - clasp - newspapers" , "Squeeze out (juice/oil)" , "Weigh" , "Crowd closely" .)
(Other definitions for main that I've seen before include "Source of electricity" , "Principal or high seas" , "Most important element" , "source of gas" , "Source of water" .)