Only a fluctuating supply (3,2)
I believe the answer is:
lay on
'supply' is the definition.
Although both the answer and definition are verbs in their base form, I cannot understand how one could define the other.
'only a fluctuating' is the wordplay.
'fluctuating' is an anagram indicator.
'only'+'a'='onlya'
'onlya' anagrammed gives 'LAY ON'.
Can you help me to learn more?
(Other definitions for lay on that I've seen before include "Provide (something)" , "instruction for Macduff" , "Provide (food, etc)" .)