Stigma involving Queen creates tense situation (6)
I believe the answer is:
Here is my best explanation:
'tense situation' is the definition.
'strain' can be an answer for 'tense' ('strain' can be a synonym of 'tense'). I am not sure about the 'situation' bit.
'stigma involving queen' is the subsidiary indication.
'stigma' becomes 'stain' ('stain' can be a synonym of 'stigma').
'involving' is an insertion indicator.
'queen' becomes 'r' (r is abbreviation regina. e.g. in ER ).
'stain' placed around 'r' is 'strain'.
'creates' is the link.
(Other definitions for strain that I've seen before include "Violent effort", "Pressure - filter", "line of ancestry", "Muscle injury, put liquid through sieve", "Tension - stock", "Breed", "Distinct breed (of animal); overexert", "Drain off", "Overwork - melody" and "Mental tension, stress".)