Relax, having forced in the plug (7,2)
I believe the answer is:
lighten up
'relax' is the definition.
(to lighten up is to relax or be less serious)
'forced in the plug' is the wordplay.
'forced' is an anagram indicator.
'in'+'the'+'plug'='intheplug'
'intheplug' is an anagram of 'LIGHTEN UP'.
'having' is the link.
(Other definitions for lighten up that I've seen before include "Chill" , "Unwind" , "Plug in the fire" , "Relax!" .)