Instrument for blower seen regularly (4)
I believe the answer is:
oboe
'instrument' is the definition.
(type of musical instrument)
'for blower seen regularly' is the wordplay.
'seen regularly' indicates alternate letters.
'for'+'blower'='forblower'
The alternate letters of 'forblower' are 'OBOE'.
(Other definitions for oboe that I've seen before include "Double-reed wind instrument" , "Double-reed woodwind" , "bit of wind" , "blow it!" , "Slender double-reed instrument" .)