Prop having increased intensity in game (7)
I believe the answer is:
Here is my best explanation:
'prop' is the definition.
(I've seen this before)
'increased intensity in game' is the wordplay.
'increased intensity' becomes 'up' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'in' indicates putting letters inside.
'game' becomes 'sport' (I've seen this before).
'up' put within 'sport' is 'SUPPORT'.
'having' is the link.
(Other definitions for support that I've seen before include "comfort", "Bear the weight of (something)", "Champion", "Help; bear", "Provide financial backing or bolster", "second", "Give assistance to", "Uphold", "Back up" and "Provide with food, clothing and shelter, or encouragement".)