Call up sponsor to be collected (4-4)
I believe the answer is:
laid-back
'be collected' is the definition.
(both can mean calm)
'call up sponsor' is the wordplay.
'call' becomes 'dial' (as in making a phone call).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'sponsor' becomes 'back'.
'dial' in reverse letter order is 'laid'.
'laid'+'back'='LAID-BACK'
'to' acts as a link.
(Other definitions for laid-back that I've seen before include "Unhurried and relaxed" , "Relaxed (colloq.)" , "Ultra-cool!" , "Easygoing and relaxed like cabal kid" .)