Clue: Martial art's good fun struggling under a couple from Kuancheng (4,2)
Answer: KUNG FU
Explanation: Definition: Martial art
**G** (good) + ***(fun)** [anag:*struggling*] *under* [*a couple from*] **KU**(ancheng) 
*The "a couple from" is a bit vague, in my opinion, but it is obvious which "couple" of letters is required in the clue.