Try to get the rent together, but it's a pain! (6)
I believe the answer is:
stitch
'it's a pain' is the definition.
(pain in the body)
'try to get the' is the wordplay.
'try to' becomes 'sitch' (I am not sure about this - if you are sure you should believe this answer much more).
'get' is an insertion indicator.
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'sitch' going around 't' is 'STITCH'.
'rent together but' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for stitch that I've seen before include "Loop of thread" , "A sewer may produce such" , "Sudden pain in side after exercise" , "Sort of pain" , "A result of running" .)