Wet pants in lake? That's unsophisticated (3,4)

'unsophisticated' is the definition.
(I've seen this in another clue)

'wet pants in lake?' is the wordplay.
'pants' indicates anagramming the letters (UK informal term for 'nonsense' or 'rubbish').
'in' indicates putting letters inside.
'lake?' becomes 'loch' (loch is a kind of lake).
'wet' anagrammed gives 'wte'.
'wte' inserted inside 'loch' is 'LOW-TECH'.

'that's' acts as a link.