Train elite unit erecting climbing frames (7)
I believe the answer is:
retinue
'train elite' is the definition.
'retinue' can be an answer for 'train' (people following someone in a procession). I am not sure about the 'elite' bit.
'unit erecting climbing frames' is the wordplay.
'erecting' shows that the letters should be reversed in order.
'climbing' becomes 'ree' (I can't explain this - if you can you should believe this answer much more).
'frames' is an insertion indicator (outside letters frame the inside letters).
'unit' in reverse letter order is 'tinu'.
'tinu' inserted within 'ree' is 'RETINUE'.
Can you help me to learn more?
(Other definitions for retinue that I've seen before include "Group attending a person" , "Group of servants with important person" , "company" , "VIP's attendants" , "Group following an important person" .)