Troubled by taking a girl back (5)
I believe the answer is:
ailed
'troubled by' is the definition.
'ailed' can be an answer for 'troubled' ('ail' can be a synonym of 'trouble'). I'm not certain of the 'by' bit.
'a girl back' is the wordplay.
'girl' becomes 'deli' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'back' says the letters should be written backwards.
'deli' back-to-front is 'iled'.
'a'+'iled'='AILED'
'taking' is the link.
Can you help me to learn more?
(Other definitions for ailed that I've seen before include "Became sick" , "was giving trouble" , "Didn't feel well" , "Troubled" , "Was ill" .)