It's card, perhaps, but very strong (7)
I believe the answer is:
drastic
'very strong' is the definition.
'drastic' can be an answer for 'strong' (similar in meaning). I'm not sure about the 'very' bit.
'it's card perhaps' is the wordplay.
'perhaps' indicates anagramming the letters.
'its'+'card'='itscard'
'itscard' with letters rearranged gives 'DRASTIC'.
'but' is the link.
Can you help me to learn more?
(Other definitions for drastic that I've seen before include "Severe and far-reaching" , "Desperate" , "Extreme - forceful" , "Extremely severe" , "Having strong effect" .)