Suspect I can't - firstly, peeping Tom will probably like it (6)

I believe the answer is:

catnip

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'tom will probably like it' is the definition.
I can't judge whether this definition defines the answer.

'suspect i can't firstly peeping' is the wordplay.
'suspect' indicates an anagram (a suspicious or unusual spelling).
'firstly' says to take the initial letters.
The initial letter of 'peeping' is 'p'.
'i'+'cant'='icant'
'icant' is an anagram of 'catni'.
'catni'+'p'='CATNIP'

Can you help me to learn more?

(Other definitions for catnip that I've seen before include "Tin cap (anag.)" , "treat for kitten" , "Feline attractor (I, not E)" , "Plant with scented leaves which felines like" , "Hairy aromatic perennial herb strongly attractive to some pets" .)

I've seen this clue in The Independent.

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