Subject to pressure in charge (5)
I believe the answer is:
topic
'subject' is the definition.
(as in a topic for discussion)
'to pressure in charge' is the wordplay.
'pressure' becomes 'p' (scientific abbreviation).
'in charge' becomes 'ic' (abbreviation for 'in charge').
'to'+'p'+'ic'='TOPIC'
(Other definitions for topic that I've seen before include "Subject matter, theme" , "Something to discuss" , "Issue (for discussion)" , "Subject (of speech, etc)" , "Theme (of, eg, a talk)" .)