Gazes open-mouthed at dog's tail and hairy paws (5)

'gazes open-mouthed' is the definition.
(to gawp is to gaze at with an open mouth)

'dog's tail and hairy paws' is the wordplay.
'tail' suggests the final letters.
'and' is a charade indicator (letters next to each other).
'hairy' indicates anagramming the letters (hairy can mean difficult or tricky).
The final letter of 'dog' is 'g'.
'paws' with letters rearranged gives 'awps'.
'g'+'awps'='GAWPS'

'at' is the link.