Jumper available to cover tip of tent's ridge pole (4-4)

'ridge pole' is the definition.
(part of a roof's structure)

'jumper available to cover tip of tent's' is the wordplay.
'jumper' becomes 'roo' (I've seen this before**).
'available' becomes 'free' ('free' can be similar in meaning to 'available').
'to cover' indicates putting letters inside.
'tip of' says to take the initial letters.
The first letter of 'tents' is 't'.
'free' going around 't' is 'ftree'.
'roo'+'ftree'='ROOF-TREE'