Uncontrolled sheep gasp (7)
I believe the answer is:
rampant
'uncontrolled' is the definition.
(similar in meaning)
'sheep gasp' is the wordplay.
'sheep' becomes 'ram' (male sheep).
'gasp' becomes 'pant' (synonyms).
'ram'+'pant'='RAMPANT'
(Other definitions for rampant that I've seen before include "Flourishing excessively as disease may be" , "Uncontrolled" , "Unrestrained and violent" , "Spreading like wildfire" , "Showing unrestrained growth" .)