With trouble mounting, is willing to participate in casual affair (7)

I believe the answer is:
liaison
'affair' is the definition.
(synonyms)
'with trouble mounting is willing' is the wordplay.
'with' is a charade indicator (letters next to each other).
'trouble' becomes 'ail' (synonyms).
'mounting' is a reversal indicator (going up in a down clue).
'willing' becomes 'on' (I've seen this in other clues).
'ail' backwards is 'lia'.
'lia' put next to 'is' is 'liais'.
'liais'+'on'='LIAISON'
'to participate in casual' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for liaison that I've seen before include "Naughty affair?" , "Communication between people or organisations" , "Bond of union" , "Communication; relationship" , "Communication between groups or units" .)
