Measure with ruler for corporal punishment (8)
I believe the answer is:
spanking
'for corporal punishment' is the definition.
(thesaurus)
'measure with ruler' is the wordplay.
'measure' becomes 'span' (span is a kind of measure).
'with' says to put letters next to each other.
'ruler' becomes 'king' (king is a kind of ruler).
'span'+'king'='SPANKING'
(Other definitions for spanking that I've seen before include "Hiding" , "Very large" , "Physical punishment" , "Lively" , "Outstanding - traditional punishment for children?" .)