Similar to barking wildly (4,3)
I believe the answer is:
like mad
'wildly' is the definition.
(I've seen this before)
'similar to barking' is the wordplay.
'similar to' becomes 'like' (I've seen this before).
'barking' becomes 'mad' (barking mad).
'like'+'mad'='LIKE MAD'
(Other definitions for like mad that I've seen before include "With furious enthusiasm" , "Furiously" , "wildly" , "Energetically" , "With great intensity, energy, or enthusiasm" .)