Consult old patient about earth recording (5,8)
I believe the answer is:
video cassette
'recording' is the definition.
'consult old patient about earth' is the wordplay.
'consult' becomes 'vide' (instruction used to direct a reader elsewhere).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'patient' becomes 'case' ('case' can be a synonym of 'patient').
'about' is an insertion indicator.
'earth' becomes 'sett' (both can refer to an animal's underground home).
'case' placed around 'sett' is 'cassette'.
'vide'+'o'+'cassette'='VIDEO CASSETTE'
(Another definition for video cassette that I've seen is " Tape for recording TV programmes".)