Sustain popular copper on run (5)
I believe the answer is:
incur
'sustain' is the definition.
(I've seen this before)
'popular copper on run' is the wordplay.
'popular' becomes 'in'.
'copper' becomes 'cu' (chemical symbol).
'on' means one lot of letters go next to another.
'run' becomes 'r' (cricket abbreviation).
'in'+'cu'+'r'='INCUR'
(Other definitions for incur that I've seen before include "Become liable to (something) through one's actions" , "Sustain" , "Become liable to (eg, a penalty)" , "Risk" , "Take on (obligation)" .)