Exercise before heading for something to drink (5-2)
I believe the answer is:
press-up
'exercise' is the definition.
(I know that press-up is a type of arm exercise)
'before heading for something to drink' is the wordplay.
'before' becomes 'pre' (prefix meaning 'before').
'heading for' says to take the initial letters.
'to drink' becomes 'sup' (to sup is to drink).
The initial letter of 'something' is 's'.
'pre'+'s'+'sup'='PRESS-UP'
(Other definitions for press-up that I've seen before include "Gymnastic floor exercise" , "PE exercise" , "Keep-fit exercise" , "Form of arm exercise" , "Face-to-the-floor exercise" .)