Once outside the low, marshy land, quite indecisive (2,3,5)
I believe the answer is:
on the fence
'quite indecisive' is the definition.
'on the fence' can be an answer for 'indecisive' (similar in meaning). I'm unsure of the 'quite' bit.
'once outside the low marshy land' is the wordplay.
'outside' indicates putting letters inside.
'low marshy land' becomes 'fen' (I've seen this before).
'the'+'fen'='thefen'
'once' placed around 'thefen' is 'ON THE FENCE'.
Can you help me to learn more?
(Another definition for on the fence that I've seen is " unwilling to commit oneself".)