Desperate to survive on scrap (4,5)
I believe the answer is:
last ditch
'desperate' is the definition.
(I've seen this before)
'survive on scrap' is the wordplay.
'survive' becomes 'last' (synonyms).
'on' means one lot of letters go next to another.
'scrap' becomes 'ditch' (I've seen this before).
'last'+'ditch'='LAST-DITCH'
'to' is the link.
(Other definitions for last ditch that I've seen before include "Final resort" , "Where to make final stand" , "resistance ends here" , "desperate attempt" , "ultimately desperate" .)