One swamp recalled in desert (4)
I believe the answer is:
gobi
'desert' is the definition.
(Gobi is an example)
'one swamp recalled' is the wordplay.
'one' becomes 'i' (Roman numeral).
'swamp' becomes 'bog' (both can mean a wet or marshy area).
'recalled' is a reversal indicator.
'i'+'bog'='ibog'
'ibog' in reverse letter order is 'GOBI'.
'in' acts as a link.
(Other definitions for gobi that I've seen before include "Desert, cauliflower in Indian cuisine" , "Desert in east Asia" , "Large desert plateau of southern Mongolia and northern China" , "Arid region in central Asia, and 38 across" , "Asian desert region" .)