Composure of bishop getting a puncture (7)
I believe the answer is:
balance
'composure' is the definition.
(thesaurus)
'bishop getting a puncture' is the wordplay.
'bishop' becomes 'b' (abbreviation used in chess).
'getting' means one lot of letters go next to another.
'puncture' becomes 'lance'.
'b'+'a'+'lance'='BALANCE'
'of' is the link.
(Other definitions for balance that I've seen before include "Weighing apparatus" , "Equilibrium or steady position" , "Scale for weighing" , "emotional stability" , "It weighs - the remainder" .)