Time-saving hairdo? (5,3)
I believe the answer is:
short cut
'hairdo?' is the definition.
Both the definition and answer are singular nouns.
Perhaps you can see a link between them that I don't see?
'time-saving' is the wordplay.
'time' becomes 'short' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'saving' becomes 'cut' (I've seen this before).
'short'+'cut'='SHORT-CUT'
(Other definitions for short cut that I've seen before include "Number one" , "crew, possibly" , "time-saver" , "Means of saving time or effort" , "Easier way" .)