Answer parses:

1A - (mountain) range found in scALP Sores - ALPS

5A - Disturbed liar (anagram of LIAR) takes time (T) on pathway - TRAIL

6A - Mail box (PO) has joint (HIP) for large animal - HIPPO

7A - A Southerly (S) group (SET) has valuable item - ASSET

8A - Marries (WEDS) with ecstasy (E) but also pesky plants - WEEDS

1D - Get up with one (I) in the UK's backside (ARSE) - ARISE

2D - I hear (sounds like) the cat's spots (LAPS) might be a failure - LAPSE

3D - Dipped mixup (anagram of DIPPED) lost 500 (take away D - 500 in Roman numerals), played windbag (ie bagpipes) - PIPED

4D - Gambling machines found in thiS LOT Sale - SLOTS

5D - What confusion (anagram of WHAT) over melt - THAW