Get back! Ian and Reg going crazy! (6)
I believe the answer is:
regain
'get back' is the definition.
(I've seen this before)
'ian and reg going crazy' is the wordplay.
'and' means one lot of letters go next to another.
'going crazy' indicates an anagram.
'ian'+'reg'='ianreg'
'ianreg' anagrammed gives 'REGAIN'.
(Other definitions for regain that I've seen before include "Get back, recover the use of" , "Take back (the Ashes, for example)" , "Recover, retrieve" , "Get back (previously owned object)" , "Recover - in gear (anag)" .)