Shortage of water could be difficult in outskirts of desert (7)
I believe the answer is:
drought
'shortage of water' is the definition.
(I've seen this before)
'difficult in outskirts of desert' is the wordplay.
'difficult' becomes 'rough' ('rough' can be similar in meaning to 'difficult'**).
'in' indicates putting letters inside.
'outskirts of' means to remove the middle letters.
'desert' with its middle taken out is 'dt'.
'rough' inserted within 'dt' is 'DROUGHT'.
'could be' acts as a link.
(Other definitions for drought that I've seen before include "Long water shortage" , "Prolonged shortage of rainfall" , "Severe water shortage" , "Period of abnormal dryness" , "Period of low rainfall" .)