Penalties may follow this special sentence (5,4)
I believe the answer is:
extra time
'penalties may follow this' is the definition.
The definition suggests a singular noun which matches the answer.
'special sentence' is the wordplay.
'special' becomes 'extra' (synonyms).
'sentence' becomes 'time' (a prison sentence).
'extra'+'time'='EXTRA TIME'
Can you help me to learn more?
(Other definitions for extra time that I've seen before include "Additional period of play" , "play's extension" , "may lead to penalties" , "Extension to match" , "this could lead to a shoot-out" .)