Understanding one initially cunning strategy (6)
I believe the answer is:
tactic
'strategy' is the definition.
(thesaurus)
'understanding one initially cunning' is the wordplay.
'understanding' becomes 'tact' (I've seen this before**).
'one' becomes 'i' (Roman numeral).
'initially' says to take the initial letters.
The first letter of 'cunning' is 'c'.
'tact'+'i'+'c'='TACTIC'
(Other definitions for tactic that I've seen before include "Ploy, strategem" , "element of strategy" , "Device" , "Action designed to achieve a specific end" , "Manoeuvre designed to outwit enemy" .)